It also is a lot less believable. And if easier to remember is pushed too far, it dumbs down the game. This may be such an area (oozes, not Reflex saves).
As an observation on such, incidently, because I didn't mean to make a possible derailer...
Big things being easier to hit is more of an AC thing. Reflexwise, if they're slow and clumsy, they'll have bad Reflexes anyway.
Fortitude...I'm leery about "bigger=tougher". It works better with dragons than elephants.
Worth raising the thought, however.