The short answer is giving you a causal, narrative like reason why you would want bottled water at home during a pandemic doesn't exist. The best argument is that a pandemic is an unknown shock to a system. We don't have any clear reason to put forward a causal hypothesis as to why this shock would damage the water part of our system. But we also know reasoning about complex systems is super fucking hard, and our puny human brains often fail at it (we can barely get right why slightly changing an API can cause entire systems to break). We also know humans die without water, very quickly.

Ultimately, it's your call to make.