I am a supervisor and a CDV install instructor and the best answer I can give you is EVERY CDV job should have a homerun to the N.I.D. weather it is from a room on the second floor or if it is mounted in the basement at the point of entry.
I dealt with this issue early in the days of CDV and I found the ONLY way to avoid liability and charge back issues is to do it the right way if your installers dont want to do it this way maybe you need some new guys.
I have found the best thing to do is cover your ass because if the house burns down or someone is assaulted or worse and the alarm doesnt work because of your guys...... YOU will be the guy on the six o'clock news having to answer those hard questions.
Best of luck!!!
This is CABL.com posting #247052. Tiny Link: cabl.co/mbcqS