How can I delete old iMessages from iCloud on iPhone and iPad?

Hi,

as far as I could investigate I am not the only one having this issue.

Situation:

Using iPhone and iPad, both logged in to the same Apple account.

iCloud shows a majestic amount of 215.402 iMessages stored. Bummer!

But, actually there is neither a fraction of this number on iPhone, nor on iPad. Strange thing is, that on the same conversation on iPad it shows a different number of “images in iCloud” than on the iPhone.

How can I delete these obviously very old messages? Isn’t this a severe data security thing? Or this is iCloud-behavior somehow intended?

Maybe someone could explain…

Thanks! 🙏🏻

[Re-Titled by Moderator]