It happened in 2016, 2018, 2020, 2022, 2025 and 2026, so 6 out of last 11 years. Not sure if I would count it as too rare.
Although I didn't claim "twice every year like clockwork" in my top-level comment either. It's just a very basic statement of the base rate.
Make it eight-times every four years or sixteen-times every eight years. Or maybe "Four-times every other year, in a clustered fashion".
I don't think any of that really changes the point.
It's more noteworthy when it happens the more clustered it tends to be. If it were typical that we'd go ~7 years with none then have ~16 in a single year, it would be huge news when it happens.
Markets move. Sometimes they move more than normal. This is one of those times.
Will it keep moving? Will it crash? Maybe! But what it has done right now is not that.