I think these people have no idea what it takes for companies to achieve high market cap values. Obviously, most companies have never had a total market cap of $250B but yet some think it's easy for Apple to simply tack on another $250B to reach that elusive $1T mark. Just a few months back there were people claiming both Amazon and Alphabet would beat Apple to that $1T market cap. I guess it's possible with big investors happily throwing immense P/Es on companies based on vague future performance. Take Microsoft with its P/E of 30 or so. Seriously, how does it earn that P/E when Apple doesn't. Based on fundamentals it definitely doesn't work. Nothing in Microsoft's fundamentals are that much better than Apple's to warrant such a high P/E. I understand Amazon is highly valued for its ability to ruin every other retailer in the U.S. so at least that makes some sense.
I don't know if Apple will reach that $1T mark and I really don't concern myself about it. As long as Apple continues to boost dividends I'll be satisfied. A $1T market cap probably isn't sustainable so I'd rather Apple just reach a sustainable level and stay at that mark for a couple of years.
You might be misreading the fundamentals. PE is a trailing indicator, it is based on the last four quarters, three of which for Apple have been declines in earnings. If you look at PEG, the forecast of multiples vs. anticipated earnings growth, MSFT and AAPL are within hailing distance of each other.
Also, while you are right not to be concerned with magic numbers such as trillion dollar market caps, you are still subscribing to magical theory when it comes to a "sustainable" market cap. Market caps that don't grow are dead stocks. You really should not want to own one. Nobody else does.