I don't think this is a bullish indicator.
The more money is locked up in a single place, the greater the centralization risk.
If Greyscale goes under, that would be catastrophic for the industry.
That would only be a bearish factor
if they went under. The centralization risk itself doesn't have a bearish effect on prices.
As I've said before, part of this (possibly even most) is arbitrage pressure. The premium over spot is only half what it used to be, so somebody has been buying their private placements while selling on the open market.
Still, Grayscale is obviously buying a notable amount of BTC. We probably shouldn't ignore the underlying demand that could signify, my theory about arbitrage aside.
Didn't dig much into it, but the way I understand it, Grayscale does actually buy and hold bitcoin(they've been buying a crap ton of mined bitcoin in the past few months), but people don't buy actual bitcoin through their bitcoin trust(GBTC).
Grayscale buys BTC, then they issue GBTC shares against them, which they sell to investors at NAV. But those investors can't sell for a year. That's why there is a big disparity between GBTC and spot prices.