Not disagreeing, simply stating users should be aware and get a say (an option would be fine to opt in to early release access), especially if they’re a paying customer.
I hear where you're coming from, but from my experience, the canary phase usually lasts less than an hour. And the traffic is usually split randomly, so the same 2% of users aren't at elevated risk for every deployment. I don't know how Slack does it, though.