I keep checking basically hourly for updates. It seems this update is genuinely a "core" update, as SEMrush is reporting pretty consistent volatility throughout all types of industries. Will be interesting to see what Marie Haynes says about it.
Edit: 8th MAY
- Early signs are suggesting it's E-A-T related. Again.
- Some correlation to thin content
May be unrelated, but website's with monstrous backlink profiles seem to be not affected (in my main industry). Which I guess, again, would be the A in E-A-T.