If God is immutable, how is creation not a change in God?

In what way is creation understood not as a change on the part of God when God is understood to be immutable? By immutable I mean the classical definition where God has never changed and never will change. Aquinas understands God to be immutable absolutely on the part of natural reason in the Summa Contra Gentiles. This appears to follow from the classical philosophical tradition. Yet some would claim that God creating has to amount to some change on his part, which hence would conflict. The question (https://christianity.stackexchange.com/questions/99339/if-there-was-a-beginning-to-gods-creations-did-god-therefore-change) covers a a related but distinct concept. That question is if creation had a start, did God change? The classic answer to that is God is not subject to Time, which he created, but rather is eternal (eternity admitting not of progression but only sequence) so creation occurred exactly as God willed eternally. Note also that question does not assume the immutability of God; presumably answers could be offered that either justify based upon God being immutable or with God being changeable in some manner (especially since the question is "did God change" not "what is the evidence that God did/did not change") This question is rather assuming the immutability of God, in what way is creation not a change. That is, it assumes an attribute of God and assumes a particular result.