The simple answer is that Christ, in fact, did not will anything that did not conform to the divine will of His Father, the key word being "conform." Christ's human will conformed to the will of His Father. And that's precisely how Augustine responded to Maximinus...
Augustine (354-430) to Maximinus: We too admit an incomparable agreement of will and of undivided charity in the Father and the Son and the Holy Spirit, because we say that this Trinity is one God. But, on account of one and the same nature and substance, we also say what you do not say, These three are one (1 Jn 5:7) [my note: Some think Augustine here cited a portion of the Johannine Comma]. If you make these distinctions and stop being so contentious, you will see that you made no answer here, and you will remain silent on this question. John E. Rotelle, O.S.A., ed., The Works of Saint Augustine, Arianism and Other Heresies, Answer to Maximinus the Arian, Book II:XX.1, Part 1, Vol. 18, trans. Roland J. Teske, S.J. (Hyde Park: New City Press, 1995), p. 301.
Latin text: Etiam nos quippe incomparabilem consensum voluntatis atque individuae charitatis Patris et Filii et Spiritus sancti confitemur, propter quod dicimus, Haec Trinitas unus est Deus. Sed nos hoc etiam, quod vos non dicitis, dicimus, propter unam eamdemque naturam atque substantiam, Hi tres unum sunt. Haec si discreveris, et contentiosus esse nolueris, non te ad ea respondisse aliquid jam videbis, et de hac quaestione procul dubio jam tacebis. Contra Maximinum Haereticum Arianorum Episcopum, Liber II, Caput XX, §1, PL 42:788-789. In the Latin text, Migne offers no indication that “Hi tres unum sunt” is a scriptural citation as he does elsewhere with scriptural citations.
Augustine (354-430) to Maximinus: The Son said to the Father, But not as I want, but as you want (Mk 14:36). Why does it help you to add your words and say, “He showed that his will was truly subject to his Father,” as if we denied that the human will ought to be subject to the will of God? One who looks a bit attentively at this passage of the holy gospel quickly sees that the Lord said this in his human nature. He said, My soul is sad even unto death (Mk 14:34). Could this have been said in the nature of the only Word? Why should you, who think that the nature of the Holy Spirit groans, not also say that the nature of the only-begotten Word of God could be sad? Still, lest someone should say something of the sort, he did not say, “I am sad,” although, even if he had said that, it ought to have been understood only of his human nature. He said, My soul is sad, and as a man he had a human soul. Nonetheless, in saying, Not as I want, he showed that he wanted something other than the Father wanted, something that he could only do with his human heart, when he changed our weakness, not into his divine, but into his human love. If he had not assumed human nature, the only-begotten Word would in no sense say to the Father, Not as I want. That immutable nature could never want something other than what the Father wanted. If you would draw these distinctions, you would not be Arian heretics. John E. Rotelle, O.S.A., ed., The Works of Saint Augustine, Arianism and Other Heresies, Answer to Maximinus the Arian, Book II:XX.2, Part 1, Vol. 18, trans. Roland J. Teske, S.J. (Hyde Park: New City Press, 1995), p. 301.
Latin text: Ubi autem dixit Filius Patri, Verum non quod ego volo, sed quod tu vis; quid te adjuvat quod tua verba subjungis et dicis, Ostendit vere voluntatem suam subjectam suo genitori: quasi nos negemus, hominis voluntatem voluntati Dei debere esse subjectam? Nam ex natura hominis hoc dixisse Dominum cito videt, qui locum ipsum sancti Evangelii paulo attentius intuetur. Ibi enim dixit: Tristis est anima mea usque ad mortem (Matth. XXVI, 39, 38). Numquid ex natura unici Verbi posset hoc dici? Sed homo qui putas gemere naturam Spiritus sancti, cur non etiam naturam Verbi Dei unigeniti tristem dicas esse potuisse? Ille tamen, ne quid diceretur tale, non ait, Tristis sum; quamvis etiamsi hoc dixisset, non nisi ex natura hominis oportuisset intelligi: sed ait, Tristis est anima mea; quam sicut homo utique habebat humanam. Quanquam et in hoc quod ait, Non quod ego volo; aliud se ostendit voluisse quam Pater: quod nisi humano corde non potuisset, cum infirmitatem nostram in suum, non divinum, sed humanum transfiguraret affectum. Homine quippe non assumpto, nullo modo Patri diceret unicum Verbum, Non quod ego volo. Nunquam enim posset immutabilis illa natura quidquam aliud velle quam Pater. Haec si distingueretis, Ariani haeretici non essetis. Contra Maximinum Haereticum Arianorum Episcopum, Liber II, Caput XX, §2, PL 42:789.
As an aside, I would affirm (contra Charles Hodge) that the Lord Jesus was impeccable or non posse peccare. I know that some folk often argue that if Christ was impeccable, then the 3-fold temptation of the διάβολος was less than real. But the purpose of the temptation was not to see IF it was possible for Christ to sin, but rather to prove that when confronted with temptation He would not sin.