The logic is based on the fact he likely will never be a 3 type hitter. He is classic leadoff. This is a young player still in early development, I don't mean in terms of right now necessarily. That's where the earn it comes in over time. Sal reminds me of a left handed Molitor, although Molly developed some real enough power over time. Not sure has that ability and if he does a plus.
If Yeli hits at least as well as he did last year you have multiple options with him and 3 is one of them. He should always hits for more power than a guy like Sal, should being the operative word. Yeli absolutely stunk the couple previous years to last. He like anyone else needs to earn his batting order slot.