If the idea is that it’s a national organisation, and one of the benefits of that is that rolling stock can be more easily cascaded between operators, then presumably everything will get yellow ends, to make that easier, without having to take the time to re-paint them with each cascade? I seem to recall the reason why Greater Anglia still have yellow ends with their new rolling stock is because they have a lot of level crossings on their routes, so if the rolling stock is cascaded to such a route, then it may need to have the yellow ends. Plus, just for consistency of the livery in all places, with all rolling stock, including those which don’t have the brighter lights.