That is possible, but it sounds unlikely to me.
In most cases you could add a shared cache to fix the problem - e.g. put your shared state in Redis, or in a file that is synced across servers (if its kept as state in a long running process it cannot need to be updated frequently).
Only true if none of the DB accesses are about stuff that could live as state across requests in a server that wasn't php. Sure, for some of that the DB's caching will be just as good, but for others, not at all.