Wow, Grayscale has lost over 14,000 BTC in their ETF in 3 trading days (619k to 605k). This BTC has to be dumped on the market. One would assume almost all of those proceeds would be moved to another Bitcoin ETF but hard to know and may be a drag on the market. 
Discussion
Apparently it’s a 2 business day lag for the ETF buys. So any shares purchased today, the spot Bitcoin will be procured on Thursday. I am not sure if it’s the same for sells but I don’t see why it wouldn’t be.