Assuming you aren't recommending always pushing to the red line before shifting up a gear, what makes you so confident that my car must have a higher ideal shif

Assuming you aren't recommending always pushing to the red line before shifting up a gear, what makes you so confident that my car must have a higher ideal shift point than ~2000rpm, is there some rule of physics that prevents engines being made to optimise around that point? Anecdotally I don't feel any difference in the gear shifting whether I upshift when the dashboard suggests or if I don't do it until, say, 4000rpm (though obviously do notice the different in the driving before the gear change), however if I shift up at lower revs than the dashboard suggests then I do feel a difference in the gear change itself and how easily the car seems to start in the next gear up. Like I said, I'm not remotely qualified to speak on this subject but I'm also finding it very hard to believe you're correct (at least, correct universally for all manual cars), so I'm going to try to do some digging around for more info.