Yeah, I got a cable to update my 2017 BMW's infotainment system, and it's OBD-II to RJ45. Doesn't seem to be too new of a thing.

Yep! Depending on the vintage, BMWs have "real" DoIP or a BMW-ized version (sort of like how KWP2000 was the predecessor to UDS). For emissions modules, they still also have to support updates over UDS as well as ENET, though, for the above mentioned J2534 reasons (Ethernet wasn't added to J2534 until 2022).