I'd guess it has to do with more dangerous magic attacks rather than physical.

Only physical AoEs I can think of off the top of my head in this raid tier are Double Attack and Earthshakers (both Neo Exdeath); just about every other raid AoE is magic (heck, there is no physical damage in O2/S at all). As for tank busters, the only physical ones are Critical Hit, and Earthshakers and Double Attack (going back to Susano his tank buster is also physical)

The majority of physical damage is from auto attacks and mini-busters (like Wyrm Tail in O1/S), which generally aren't considered dangerous enough to get the melee to think about using Feign (if you can get any PUG to even take the skill).