The experiments released to the general public should be stable. Unstable experiments are released in their canary builds.
>"The experiment/flag has been on in beta for ~5 months," said David Bienvenu, a Google Chrome engineer. "It was turned on for stable (e.g., M77, M78) via an experiment that was pushed to released Chrome Tuesday morning."
>"Prior to that, it had been on for about 1% of M77 and M78 users for a month with no reports of issues, unfortunately," he added.
The bug affected Citrix-style environments, where perhaps 10-20 users are running Chrome on the same machine. If 1% of users are running the experiment the chance of two of those 10 users running the experiment is tiny, and when they experience the bug it's unlikely to get reported back to Google.