[SPOILER FOR ECHO]
Eh? TJ's route does something for Leo's? As far as I know, the reasons as to why you should enjoy Leo's ending are just about covered in his own route; it's relatively self-contained in that way. I'd treated it as the one with the least support from other routes in delivering its climax. I'm kind of surprised that TJ's, one of the more removed from the others that does this. Can you attach a spoiler to remind me of that plot point?
Besides that, the reason why I placed the latter 2 (TJ, Flynn) in their places is their definitive reveal of a meta issue in the narrative-- the fallibility of the protagonist Chase. The other three barely touch this on their own; at best, Leo's and Jenna's left hints. The magnitude of this reveal is dependent on how much you've established beforehand. The double-take it leads you to do is a precious thing branching mystery VN's can induce. This is Echo's design, seeing how it sprinkles exclusive interconnected lore in each route. You'd miss this experience were you to stumble upon it early.
Funnily enough, my reason for doing the Carl route first is a bit similar to yours. As it is generally deemed the least impactful, one would want to deal with it first as to avoid a valley in your escalating playthroughs. As you've also mentioned, the fact that it had a lot of lore details made it even more appealing for that.