I'm sure when Joe Shuster first drew his Superman, he thought his was rather muscular. And when Curt Swan drew his Superman, I'm sure he thought he had made him a bit bigger than was realistic.
If you ask me, Superman should be in that ballpark. But comics have gone crazy with over-proportioned men--so Swan's Superman that should look like a really imposing figure seems like a normal guy by comparison. And even the Dan Jurgens/JL Garcia Lopez/Neal Adams Superman with over the top heroic proportions now seems minmally proportioned.
Superman shouldn't really have to look so muscle-bound.