Harold
That is a bad distribution design for sure.
A couple of years ago a local office building had an emergency panel upgrade. The original panel had all fused disconnects for the various emergency panels. All of the loads were coordinated to be sure the lowest rated fuse blew 1st.
When I went to inspect the replacement panel which was all breakers I discovered the panel breakers were series rated which I immediately rejected as a branch breaker could take out the main which I also made them remove once we established the fuse ahead was better coordinated and could not be coordinated with the EM panel main breaker.
The engineer said he ordered a coordinated CDP but of course did not verify the delivered breakers met the design. The wholesaler and the electrical contractor might have substituted the lower rated breakers as they were pretty pricey to have a coordinated system at the fault levels in this building.
Series rated systems can save on installation costs but coordinated systems give much more reliable protection or at least are more likely to leave the other unfaulted loads working. Never allow it on a life safety system.
