idk i used this approach and done ok competitively (e.g. htmx, me, one dude, vs react, facebook & vercel) and, as grugbrain.dev says, unit test tend to lock you in to a particular implementation

integration tests don't need to be slow on modern hardware, are easier to debug than end-to-end if they are kept at the right level of abstraction and catch more real-world bugs than overly-specialized unit tests w/ complicated mocks, etc