Hi @tangible,
aDAI from Aave V2 and Matic maDAI are two different things
You can use the AaveGotchi bridge to transfer your aDAI(V2) to Polygon to get maDAI
maDAI are aDAI(v2) bridged to Polygon ≠ amDAI which is the aDAI of the Aave Polygon Market
You can get amDAI by bridging DAI to Polygon (via your Matic wallet or zapper.fi) then depositing the DAI on Aave Polygon Market