Not fully. It requests a desktop layout but sites still know you're on a mobile browser, hence sites that explicitly block mobile browsers will show the same "this page only viewable on desktop" message. Actual user agent switcher extensions don't have that problem.

It does change but it only removes the "mobile" part from user agent (through sniffing). But I think he's referring to a broader usage, for instance: MS Teams only works on Chromium-based browsers and Safari, so user agent change façade comes in handy for this.