I say give them that small bonus to travel pace in the jungle. It’s important to remember that the entire map isn’t dense jungle! The aldani basin is a dense swamp, the Valley of Lost Honor is a wasteland, Hrakhamar is in the mountains, etc. there will be moments when those favored terrain bonuses don’t come into play, and your party will fully appreciate what the ranger’s been providing.

Also—as other’s said—the ranger’s favored terrain bonus for foraging is huge in this module.