My logic here is that those two entities act more like player entities and less like projectiles. Both of them can be hooked by Roadhog's Chain Hook for example, and I think they can also be stunned, trapped by a Junkrat's Steel Trap or get caught in Zarya's Graviton Surge. In Junkrat's case, the player even takes control over the "projectile"! So how are those entities treated when it comes to Symmetra's Teleporter? Can Junkrat's Rip Tire use the Teleporter? Can a traveling D.Va Self-Destruct use the Teleporter?
With the most recent Symmatra rework, where her teleporter is now a standard ability, both a rogue tire and an unpiloted mech can travel through it. The player controls whether the tire does, using the same interact button as by themselves, while the mech does by itself if boosted into it or the teleporter appears underneath it.
(Back when the teleporter was an ultimate, neither of these things could use it.)