Read some things online that says they are just rebranded hubs.

Looking at getting some boost 29er wheels, but run a SRAM XD fitment cassette currently – mental debate – buy wheels and change standard Shimano fitment Giant freehub to DT Swiss XD freehub and have the cassette swappable, or buy wheels and fit Shimano cassette?

(currently running 650b+ wheels with Boost Hope Pro 4’s)

It depends, many higher model spec giants run factory wheelsets. , spline 1501 etc. Stickered Spline 1501 will of course be star ratchet freehub.
Being that they offer DT branded factory wheels, I very much doubt that they would stick giant stickers over a DT Swiss product. If they did, it would be 370 model hubs with 3pawl hubs.
Syncros/Scott do rebranded DT Swiss, but even the carbon factory wheels are rebranded.

Giant certainly did use DT240 star ratchet internals in some of their hubs, dunno if they still do. Specialized/Roval and Bontrager both use them too. The former fit the upgraded star ratchets as stock too.

Using quality components in house brands enhances the reputation of those house brands. They can then be considered as more than just OEM kit.

The P1 wheels do still use DT 240 internals, technically not quite the same as rebadged, but who cares about the hubshells?!

That obviously won’t be the case for all Giant wheels though.

Their P-SlR road wheels are branded DT and Giant. Their cheaper wheels are Giant branded hubs.