I'm not just talking about the UK though, and the pattern seems to differ between countries and even times - if it was simply capacity then I'm not convinced the impact would be high when cases were relatively low.
On susceptibility profile - should this change ICU to Deaths? Wouldn't it just increase the susceptibility over the population - the same as your age profile does?
It could be a data recording issue, the Belgium one there is pretty unlikely with the up/down waves over weekly periods, so it could be some sort of artifact in the recording.