It's optimized as far as Microsoft is concerned. It's pointless to argue over this, really.
"Games featuring the Optimized for Xbox Series X|S icon will showcase unparalleled
load-times, heightened visuals, and steadier framerates at up to 120FPS. These include new titles built natively using the Xbox Series X|S development environment
as well as previously released titles that have been rebuilt specifically for Xbox Series X|S."
Optimized for Series X|S | Xbox
Mass Effect falls under that category of "previously released titles" (back compat) taking advantage of the hardware of X|S.