I think the benefit is marginal since compared to harddrives bios flash memory almost never fails and recovery solutions for a bad update are readily available. So this sounds like a bad excuse again.

I work on embedded systems and even the really cheap memory never fails on quantity of thousands of devices if it isn't regularly written to. I has become extremely reliable. Self-checks are still in place of course.

In any case it should not prevent external booting or if it does Apple should just supply the needed files for sensible restore options.