Schwab gave me a little different explanation ..not sure what is true , but what they told me ..

If cash account no problem , they don’t loan your shares .

But if a margin account as I have , they said ,
if you have anything on margin they do it , if you don’t have a margin at the time they don’t .

I remember this well as I had at the time few thousand dollars on the margin , I was very upset , so I send them the money , and since then I have not a one doll margin ..

This how they explained to me .
So I don’t know ..