If this were true,

It is.

they wouldn't have to settle any claims on older properties
which, by definition, are all suffering from gradually
operating causes

Nonsense.

You can't claim for gradually operating causes, which is effectively code
for "wear and tear", like needing to repaint windows due to weathering, or
needing to renew pointing.

You can claim for non-gradually operating causes, like subsidence, a tree
smashing into the bedroom, a lorry in the lounge, storm damage or flooding.

Christian.