It's less about muscles and more about exaggerated proportions for the character. I mean, those were all for the same book:
https://vignette.wikia.nocookie.net/...20160120194523
https://comicshop.tmcgraphics.com/wp...rs_Vol_4_6.jpg
https://thegeekiary.com/wp-content/u...15-008-007.jpg
https://thegeekiary.com/wp-content/u...Avengers16.jpg
https://thegeekiary.com/wp-content/u...8-666x1024.jpg
https://img.fireden.net/co/image/145...5108257923.jpg
One of those things is clearly not like the others, which is why Sandoval's take stands out as the ''wrong'' way to portray the character. I'm fine with the way he's drawn on Strikeforce, but you gotta admit that the Strikeforce art STILL doesn't make him look like Sandoval's Billy.