Mp3Tag starts preminimized to taskbar if it was finished from minimized-to-tray or minimized-to-taskbar state during the session before. In other words the program remembers its last state although it looks unfunctional for me.
Sorry, but this is not a very helpful comment. I also don't like the start minimized feature. I don't typically check whether a program is minimized or not when I close it, but I can't think of a reason why I'd ever want this particular program to open unless I intended to actually work with it. So I find it particularly annoying that I have to restore it every time I open it.
I have the impression that you have not yet explored the feature in depth:
Mp3tag comes up in the mode in which the user (!) closed it.
close it maximized -> next start opens MP3tag maximized.
close it in restored mode -> next start opens MP3tag in restored mode.
close it minimized -> next start opens MP3tag minmized.
So it could very well be that there are users who prefer the maximized mode, while others prefer the restored mode ... You have the choice and Mp3tag respects it and does not overrule a user input.
BTW: this has been rated as no bug 7 years ago. So in the meantime it has become a feature. There is no bug.