Encumbrance rules no matter the edition never stand-up to much scrutiny. Best leave that out of the discussion. Using Dex to 'jump' should be like watching Jackie Chan get around, over, and up walls gaps etc. He needs multiple things to work around because the distance is too far for him to Athletics(Str) his way across. At least that's how I see it.
Something like that doesn't seem possible in BG:3, most heavy duty platformers don't even manage it.
The distance is too far for anyone with any amount of human strength to jump. It's a game where things are larger than life and real world physics are set aside in favor of a version that is stretched and slightly warped to accommodate for fun and entertainment.
The encumbrance rules showcase this perfectly. All the arguments about "muscles in legs" are out of touch. It's a cherry picked moment to appeal to real world physics, nothing more.
The game is designed around the element of having fun, within reasonable boundaries. A character can't, for instance, jump over a building, but they can jump over a table. Okay, that's still an incredibly long jump, but whatever, it's more fun for positioning during combat and such, and it's not breaking the bank of verisimilitude.
But once someone starts going on about "muscles in legs," things get inherently pedantic and boring. Again, completely out of touch with the system and what it's trying to accomplish, which is to say that it's trying to provide an encumbrance system that both limits and allows.
It's fun to have a character with high strength jumping around the map. Equally, it would be fun to have a character with a high dexterity jumping around the map, in the tradition of swashbuckling heroes leaping here and there and swinging from chandeliers. One character can hang their hat on Athletics while the other swears by Acrobatics. Whatever. We're working with an imperfect system and just trying to have fun.
