Using /32 vs /24 for Endpoints on a /24 Subnet?

I feel like this is a terribly basic question, but when I try to look up the answer, all I find is posts referring to Subnetting. On my firewalls, I originally was instructed to use 192.168.40.X/32 (255.255.255.255) for each endpoint, which seemed odd to me, as previously I had always used a /24 (255.255.255.0) for endpoints.

I understand how subnetting works, but I am struggling to understand why I need to use a /32 when adding firewall addresses? From my research, it appears that would only be pertinent if the endpoint never had to communicate with anything else on the same subnet (such as a gateway address/loopback).

Again, I feel this is something I should already know, but I have had zero "formal" training, and learned on the fly. Is it proper to use a /32 for endpoints on a /24 subnet, or am I thinking of this the wrong way?