Ronnie is far from the hardest or best conditioned BB of all-time.
On average, no, but Ronnie at the 98 Olympia (his dryest ever) could at least tie for that distinction:

I don't think I have ever seen pecs quite this striated

when a bodybuilder has the "skeleton face "look, you know he is about as dry as you can get..

you won't find a back shot that was dryer that this.
Perhaps only munzer was dryer.
and yes, that ironager comparison is a really, really bad shot of BOTH Ronnie and Sergio.