I believe you might be right RS.
I have had USB sticks fail before doing this, they seemed to work ok other wise.
Sometimes using an older USB stick worked just fine, and new ones didn't.
Could also be a driver issue, meaning I have a USB stick that works fine in Win 10, but a Win 7 setup cannot read it. Win 7 setup can read an older USB stick ok, just not the news ones.
Its hard to say with USB sticks these days, often they are cheaply made and what ever standards they use for these sticks are simply over ruled by a cost factor. The EasyStore review I did that came with a 32GB USB stick which died after two removals, yes I eject USB sticks every time. It simply died.