I don't really have a set opinion on this, but one downside I see is that thus loading a large file could potentially feel slower, because the main window would pop up *before* it gets loaded. Also, note that this affects virtually *all* CLI openings, as the main window is unlikely to be focused when that happens.
I get that this tries to "fix the problem everywhere", but is it the only possible reason for this to happen? And if it's not bulletproof, can't we "just" fix the offending case(s) not to be buggy in that regard? (using the document ID or document pointer, etc.)