It always puzzles me how apparently well known flaws never mentioned by product reviewers, even genuinely pro-consumer and generally well respected, like rtings or notebookchecks.
You buy product after stellar review, encounter problem, search for solution, find reddit thread where everyone is "yeah, it is always like that, why do you act surprised?"
Why indeed?
It's not trivial to find it, you need to set it to dGPU only mode via mux switch and then let the LatencyMon test running for more than 120seconds.
(I'm not sure if it lags in igpu pass-through mode)
notebookcheck does report latencymon numbers and even remarks when it says the laptop is not recommended for real time audio:
https://www.notebookcheck.net/The-RTX-5090-Laptop-and-mini-L...
They don't see these extreme values though.
I really never did this question to myself, but if will happens I would start, trivially, looking for who sponsor those review sites.
Usually their revenue is from affiliate links. YouTube channels have ad spots, merch sales etc. There are many shills of course, but some are doing their best to give accurate reviews and don't shy away from bashing manufacturers for their missteps.
Yet widely known (to enthusiasts) problems, like stutters from the OP, are often not mentioned at all.
LinusTechTips doesn't depend on ASUS money in any meaningful way, but still failed to mention stutters in their Zephyrus G16 review. Some might say LTT is not a reviewer, he is an entertainer, but he undeniably thrives to be accurate while doing so.