Prince of Persia came out in 1989, while Flashback arrived in 1992. In the late 80s and early 90s, pc video game tech was evolving at a breakneck pace, a 3-year gap was an eternity. Prince of Persia ran quite well on an 8-bit XT, Flashback needed a 16-bit 286. They are basically from a different era, and Flashback was surely inspired by PoP.
The 8088 had an 8-bit data bus, but I don't think I would call it (or the XT) "8-bit" overall. By the same logic, a 386SX or 486SLC is "16-bit".
Fair point