They integrate GPS/GNSS, Iridum and other satellite signals.
I would bet a billion dollars that this has nothing to do with their existing products and everything to do with the rumored Apple Car. Centimetre accuracy location services would be a very useful feature for auto driving capabilities.
Even if it were, why would you design it to require sub-meter, externally-provided precision, especially when there are guaranteed to be circumstances (e.g., tunnels) where it won't be available?
My guess is that Apple wants faster locking GPS because faster locking means less time with antennas cranked up using power.
Put better GPS antennas in your phone then. GPS chipsets in your typical Samsung and iPhone are already capable of centimeter resolution, its the shit antenna they put inside that's the problem.
https://radionavlab.ae.utexas.edu/images/stories/files/paper...
As far as I know, the iPhone doesn't contain an antenna per se, rather they use the frame of the phone as the antenna. I believe many other phones do this too. There are some pretty clear advantages (weight, size of device) but presumably some downsides too (which is why perhaps they're buying this company).
People are always complaining about some aspect of Apple devices where there is apparently an easy solution (latest example would be Apple Watch water-proofing) but there is always a downside, even if it isn't clear - otherwise Apple would have done it. The problem is the compromise and where you draw the line.
Given you can't rely purely on GPS with autonomous vehicles anyway (tunnels, highly built up areas etc) I would have through the current accuracy was fine.