there is also a bit of fee pressure, some of the btc etfs have fees of 0.2% while gld is 0.4%

In all probability yours is the right explanation. However it also occurs to me that I wonder if the competition against BTC ETFs is putting pressure on the GLD issuers to play less rehypothecation games. I notice that both Silver and Gold has been on a tear since Jan.

Perhaps they realize that GLD needs to compete.

freetx

charts_and_numbers

World’s Largest Gold ETF Holdings Down 5% Since Bitcoin ETF Launch

This kinda makes sense. People like gold as a stabilizer, right? If the price goes up, they'll want to rebalance