Why does borrowability of shares inversely correlate with probability of assignment or exercise? I transcribe 5:26 of this video. I don't know that YouTuber's credentials.

So looking back here, what could possibly
cause you to get assigned early? If we
look right here, AMD shares are listed as easy to borrow.
That's really important to know,
and it means that the risk of early
assignment is almost non-existent.


If we put something like Tesla in,
they're listed as hard to borrow
and that slightly elevates your risk. If
shares are harder to borrow, calls are
more likely to get exercised, which puts you in a position where you
could be hitting max loss early on account of early assignment like we
just talked about. And there's some
smaller OTC stocks things like this [the YouTuber is pointing to ticker symbol TSOI] that
are less not available to borrow. These, pretty much the second that
they're in the money, are going to be
exercised so that's the risk that you
earn right there.
I disagree with the author's premise. The primary reason that options are exercised early is because of discount arbitrage (an ITM option trades below its intrinsic value) or there is a dividend arbitrage in an ITM put (the time premium is less than the dividend, NOT the call).
No one with a lick of sense would exercise an option that has time premium remaining because that would be throwing away the time premium and incurring more transactional costs (B/A spread and commissions if you're still paying them).
I listened to another minute of the video and I think that the author really has no clue. He talks about the possibility of an OTM short option being assigned early because of a dividend. Now who wouldn't want that to happen to them? If the stock is \$102 and I'm short the \$105 call, please, make me sell the stock to you for \$105! It makes no sense at all.
He continues his errors with another example. A stock is \$101 and you are short a \$100 call that's worth \$2. The company announces a \$2 dividend and the call owner exercises and you are assigned. Why in the world would he do that? He could sell the call for \$2 and buy the stock for \$101. Exercising throws a dollar of time premium away.