I started working in MA and, when I moved to AZ, worked remotely from AZ (your second scenario).
My understanding is that MA taxes all income received from MA sources, even by nonresidents. From an MA state website: "Non-residents are taxed on items of gross income from sources within the Commonwealth, including income derived from or connected with any trade or business, including any employment, in Massachusetts. M.G.L. c. 62, § 5A." It is unusual in this regard but it does do that.
And my understanding is that Arizona allows a credit against these taxes paid IF the other state, like MA, does tax nonresidents on MA source income.
So on my reading, my AZ income is ~80k (amount earned while resident in AZ) but my credit should be the amount of taxes paid to MA (say $15k).
On your reading, my AZ income is $80k, MA income $20k, and I get an MA refund.
Turbotax isn't doing either of these though - it's saying my MA income is $100k, AZ income is $0.
