Unfortunately not all the fats could run PS2 games, only the CECHAxx and CECHBxx (NTSC) had the hardware to run PS2 games. The early PAL models (CECHCxx and CECHExx) had software emulation apparently, dunno if it was any good. I hunted down a fat model specifically because I wanted the backwards compatibility, can’t remember which model I ended up buying, but it was not a backwards compatible one. Very disappointed at the time, but I was still sad when it died.

Also the possiblity to dualboot Linux was patched out pretty quickly if I remember correctly, people were pretty peeved about it.