Me too, I always ask about this, and this is always suspiciously missing from every single review. I assume it just doesn’t work, otherwise we would have seen someone mention it, the steam deck’s reviews all mentioned that since it’s one of (if not the) most important feature for a handheld. For example (just rewatched it to be sure) LTT’s review doesn’t mention that on the ROG, but on the Deck the quote is

[About the sleep and come back to game feature] An Xbox, sure, but I would like to see a Windows PC do that.

So even back then they acknowledged that windows was not capable at that time of doing that (remember they had other handhelds at the time), but they never brought it up on the ROG review, which is very suspicious, almost as if Asus is trying to find a fix and preventing reviewers from talking about it. But that might be too much time hat on my side.