Insurance wouldn't cover it anyway, they'll send out an assessor and it would be very quickly identified the issue was with a lack of maintenance which is ultimately what damaged caused failed grout and sealant is. Insurance has never covered this sort of thing, otherwise if you fancy a new bathroom you'd nick a hole in the grout and wait for it to fail and hay presto, bathroom refit.
I'd be surprised if it was even tanked properly in the first place, they usually just whack tiles directly to plasterboard and call it done. As others have said, grout is the first line of defence but it shouldn't be the only waterproofing and require the whole room to be scrapped if it leaks. As a minimum there should be two layers of waterproofing before you hit something squishy.