I think people look at this all wrong. Yes there are freaks like sale who can just flat bring it. But it is intuitive and common sense that strength can only help and can't hurt. Do not confuse strength with body building. Two different things.
I'm with you and believe strength training is a very big component. Whatever works for you, do it! I wouldn't recommend anyone doing Jake Arrieta's training regimen but it works for him!
I agree with a lot of KB's teachings and know a local college player that spent some time with him last summer, the kid was ripped, very athletic to begin with and was trying to find his true ceiling, in an attempt to earn an opportunity to get more innings. We'll see in a few weeks when rotations are set as he's a middle relief that was used very sparingly in the past. Kudos to the kid for reaching out for help and getting better!
Body mass and genetics are a funny thing. I don't pretend to know anything beyond what I've seen or observed. There are some great ideas and guidance around here, some I've taken, some I've chose not to.
There is a former MTS player, current Mets affiliate that trains at the same facility as my son. He's all of 5'-9", 160lbs ringing wet and brings it at 97!!! Who can explain, it's nothing short of amazing!