Yes, that is a mistake, it would also be a huge mistake to buy this dongle, which is only HD capable, the 4K UHD with Dolby Vision support variant does not cost much more and is definitely preferable to the HD-only model. The HD-only version has far too many limitations and should definitely not be bought.

This is the "real" one with 4K Ultra HD:

Google Chromecast with Google TV 4K (Google Assistant)