It seemed that it was always implied that they were brought back remotely through their compasses which connected them to the Quantum Tunnel, which would explain why they were using the compasses to get back.
The Gps' were a connection to the Quantum tunnel.
Stark solves this with a "time-space GPS," a way for the team to
travel through the quantum bridge without getting lost in it. None of
any current science suggests that this is possible, writes Shankland.
But then he leaves the door open a tiiiiiiiny bit, giving us hope that
maybe that ugly brown van's quantum bridge was actually a wormhole
With a form of so-called exotic matter -- something with negative
energy density -- you could prop wormholes open, but nobody knows if
this is even possible, except at the minutest quantum-mechanical
What I'm hearing is that Hank Pym (the original Ant-Man, played by
Michael Douglas) and co. created a wormhole, accidentally left Scott
in it, and then the Avengers used the same wormhole and their GPS
devices to save this single universe.
Avengers: Endgame and time travel: Why it all makes perfect sense - CNET
So, the GPS' give them access to the Quantum bridge with which they can travel further back in time (to get more Pym Particles) or back to the present.