Do institutions have to sell some of their BTC when customers sell BTC-ETF shares?

Lets say i have 100k USD worth of BTC in an ETF, if I sell all of it, will Fidelity, VanEck, etc. have to sell 100k worth of BTC as well?

Seems like it would be a bit illogical, since another 100k could come in quickly.

Or maybe they only sell past a certain amount, like 10m USD?