@TomD8
From a programming standpoint, I would think that Turbo Tax (and other software providers) would 'poke yoke' the software as the average user would not otherwise know - or even follow the instructions if told - to complete the non-residential state first. In fact, is that stated anywhere in Turbo Tax's FAQ or other offical Turbo Tax postings on its website that order matters when completing multiple state returns?
From a software design standpoint, EVERYTIME any input is changed in either the non-residential state or the residential state, the software recalculates EVERYTHING. That ensures the output (both state tax returns) is correct. Given how quick and cheaply that can occur, I'd be astounded if that was not the case.
Otherwise, a user could claim that a 'calculation error' under the Turbo Tax guarentee and make TT liable for any interest and penalties that occured when the state tax return was incorrect. The user would claim that everything was input correctly and no where was he told to do the non-residential state first. And the way Turbo Tax mitigatges this risk is to just recalulate everything every time something is changed.
I'll "stand down" if there is an official Turbo Tax FAQ stating that the order the state tax return is completed matters.
Hence, while in a 'pen and pencil' world, order matters, but in a software world that risk is mitigated because of the continueal recalcuation of the inputs to derive new outputs.
