Even if it’s delta, it cannot patch itself when running on Windows. So it runs the updater, creates a new exec and switches to it after relaunch. Same as Chrome or Firefox.
Honestly I'd be all for this if the OS had a good autoupdate mechanism for 3rd party applications. But that's not the world we live in. Certainly not on windows - which is too busy adding antivax conspiracy articles to the start menu.
And with Chromium this directly leads to crashes - when you update the browser as its open, the new tabs will open with the new version of the binary, with the old ones still using the old binary - which usually leads to crash.
I prefer 'you cannot do X' instead of 'we allow you to do it, but it might misbehave in unpredictable ways'.