That’s fine and it was also fine for previous ST3 point updates. What’s not fine is showing a modal update dialog that looks exactly like previous point updates but actually upgrades the program to a version which is incompatible with the previously purchased license. Moreover, the upgraded version requires the purchase of a new license for continued use (as clearly stated on the download page).
Due to this deceptive behavior users cannot make informed decisions. As there was no action taken from the Sublime HQ team in response to the many people reporting this, one can only assume that this is very much intentional. Otherwise they would have disabled the update check by now to avoid misleading their customers. I am also very skeptical to the argument that this was an oversight. For the first major upgrade in years, the upgrade path of existing customers must have been clearly defined.
FWIW, personally I decided that the Sublime HQ team cannot be trusted anymore. Who knows what the next update will bring. This time we were lucky that many (not all) were able to downgrade to ST3 without issues. Next time they might break the configuration so no downgrade is possible anymore or change the license at will. It’s a good time to explore alternatives that actually respect their users/ customers.