Ideally, how is a block of publicly assigned IPs distributed within a single site?

I'll usually see a small gigabit switch between the modem and any given firewalls/routers to split the public addresses, example:

FiOS ONT > 5 port switch

switch eth1 > firewall1/router1

switch eth2 > firewall2/router2

switch eth3 > firewall3/router3

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My question is this: Is that the proper way to do it? Is one meant to physically add a firewall/router to handle each IP addresses that is part of the block, or can this be accomplished via a main core router/firewall that can distribute the addresses in a port-forwarding/VLAN style?

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I was reading a post on the UniFi USG Pro: (https://community.ubnt.com/t5/UniFi-Routing-Switching/USG-Pro-Multiple-WAN-IPS-mapped-to-various-internal-locations/td-p/1770942) That can handle a good block of 5 public IP addresses.

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Thanks in advance.