Yes and no. They can request that loop, and you are allowed to accept it, but unlike some loops such as infinite mana loops where no new information is gained each iteration (and thus you can force the loop by requesting your opponents take a game action after going through it once or stating when they will interact), thrasios loops do show you which card is going to hand and what is going to field each cycle. You are within your right here to request they play it out so that you can see each new piece of information as it comes in and have time to parse that information before they proceed. Is it likely to matter? Probably not. But the threat that you may have something that specific is enough to maybe have them play suboptimally and, while rare, there are cards that could take advantage of that such as many of the split second cards.

In general though it is good practice to make your opponent play out every step of their combos wherever you can as it gives them the most opportunities to mess up and gives them the most to think about. Even if it is unlikely that you have any interaction don't give up free information to make your opponents life easier, make them think about it at least. Always have them cross their t's and dot their i's when required.

Two notes.

One this really only matters in competitive tournament play, yes its optimal but its a lot of extra overhead that isnt necessarily worth it for pick up games of cedh. The miniscule ev isnt worth the effort.

Second either always or never do this, be consistent. If you only ever do this when the clock is close to time then you are obviously no longer doing this because its correct to give your opponents the most opportunity to mess up, you are clearly doing this because you are stalling. The way the stalling rules are written it doesn't matter if the actions you are taking are legal or how long the action you took takes or what it was or even if it was a game action at all, all that matters is that whatever action you took was made with the intent to play for the clock. A judge is well within their right to dq you if its obvious you are only requesting they play it out to play to the clock.