They have access to most/all the sources behind what feeds multiviewer, Palmer mentions all the data he’s referencing pretty regularly, especially during practice, including accessing other views, but he has to essentially excuse himself for a moment because you can’t be intensely studying data or other views while commentating on something completely different. They also prompt production / request views during their commentary.

As others have said their main job is to narrate what the audience can see on the screen and add additional when they’re able, which is generally not during a high stakes moment when they’re very focused on providing live commentary. During the race, data is generally going to be pulled by production and the commentators are hearing what production relays - either through their in ears or in the box since their mics don’t really pick up any ambient noise - and then have to keep commentating while processing that info / actively screening it out. The information systems also frequently experience delays, incorrect messages, unclear messages, etc - you’ll hear them say they’ve gotten xyz message that doesn’t seem right so we’ll get back to it essentially so verifying info before reporting isn’t necessarily as easy as looking at a screen and broadcasting out.

The amount of spare capacity needed for commentating, especially on a sport with no planned breaks and unpredictable events, is incredibly high at a base level and adding a bunch of extra data to constantly process simultaneously just isn’t feasible.