That does not say it took 19 minutes for alerts to appear. Following could mean any amount of time.

It's 19 minutes until active engagement by staff. And planned rolling restarts can trigger alerts if you don't set thresholds of time instead of just thresholds of count.

It would be nice though if alert systems made it easy to wire up CD to turn down sensitivity during observed actions. Sort of like how the immune system turns down a bit while you're eating.