Great find, it's pretty cool how it seems that there are still more things to discover even though I always used to think that pretty much everything has been found already.
Anyway, it indeed seems so laggy that it may only work with a bunch of guards down there and they aren't there on a speedrun, at least not that many of them. The timer even says 4 minutes something, so they had some time to gather there. Putting high-res on might work, but it still seems pretty difficult to perform, can't really tell because I've never done it, but still.