Are you sure about that? I was under the impression that this was running on N53, which is towards the bottom of S band, both directions.
The "emission type" for the satellite service is 198KG1D and operates under FCC rule Part 25 (Satellite Communications). They run 400mW or so up on 1.6GHz L-band, and ~90mW downlink S-band.
A Spot Gen3 runs around 200mW on L-band only for both ways. There's a slightly different emissions type, but same satellites.
The ground stations had additional hardware added by Cobham to support Apple's use on L/S-band.
I think Apple added n53 as part of this deal at Globalstar's request. Globalstar is trying to lease their spectrum terrestrially for small cell networks and network capacity solutions for the carriers.
https://www.globalstar.com/Globalstar/media/Globalstar/Downl... (PDF warning) Here's a presentation with some details.