The existence of the Ryzen 9 4900H APUs was first rumored back in late 2019, but now we have actual proof that the model is no mere typo, as Videocardz sources spotted a TUF Gaming laptop powered by the unannounced processor. The 45 W APU will be able to boost to 4.2 GHz, which is 200 MHz slower than the 35 W Ryzen 9 4900HS leaked earlier by Asus. Moreover, the TUF Gaming laptop appears to be missing a discrete GPU.
https://www.notebookcheck.net/Unannounced-top-of-the-line-Ryzen-9-4900H-APU-spotted-in-the-wild-on-an-Asus-TUF-Gaming-laptop.455493.0.html