Authorship is, however, and interesting and sometimes illuminating study.
Your decision on that point was based, if I recall correctly, on manuscript evidence and internal consistency of language and content. You make the same decision with regard to the longer and shorter endings to Mark. In the past you have similarly rejected the suggestion that, based on similar evidence, the pastoral epistles should be attributed to a different author to the other pauline epistles, and the authorship of some or all of Colossians and Ephesians should also be cast into some degree of doubt. You seem to know with a high degree of certainty who wrote what, and I would be very interested to know on what that certainty is based. If you do have the time, I would be very interested to know what sources, ancient or modern, inform your 'satisfaction' with the traditional attributions of authorship with regard to the four Gospels.