That seems reasonable, though if they are anticipating delays, then perhaps they should be concentrating on a revised schedule where there will be no delays and therefore no need for anyone to claim...
I imagine that there will be many things (not just aviation) that will generate the excuse, "Sorry, due to a no deal, the rules don't apply" much akin to "Sorry, Health & Safety" or "Sorry, Data Protection" without anyone actually knowing what the rules are.