@Nathan G. Thanks for your input. There is a difference between potential problem and real problem.
Since my unit is above this will always be the potential problem in every case not just this one. If I am paying either from my pocket or my tenants, I am accepting the premise that in future I will liable by default unless I can prove otherwise. The proof of fault is on me not on them.
May be I am overthinking this but I am here to learn and protect my liability. I am trying to understand process rather than determining the fault. I am happy to pay for damages if process requires me to do so.
Your point about HOA relying on plumbers report makes sense. However, if that is the case it should be their Rules and regulations and not specific to my case. Also, if that's the case are they within their legal bounds to add something like this in their rules and regulations.
I have rented in past and I have been as a tenant on this side. I remember HOA folks came to my apartment to personally supervise the plumbing. The owner discovered their problem in their unit as opposed to mine.
May be I am overthinking this but I believe bigger pockets was designed precisely for this :)