He did say intrusion detection so that's probably it. That, and if you're using any kind of complicated firewall rules, those aren't HW accelerated like enterprise gear, so throughput tanks.
This is worse with the older devices.
For example: https://www.youtube.com/watch?v=p4yKf044meY
https://community.ui.com/questions/UniFi-Gateway-Intrusion-D...
I have a udm se, 10 g3 cams, 4k bullet+ai, door entry + cam +ai, couple of the display viewports running all day and a nano hd access point and symmetric gig with intrusion etc turned on. I also have wireguard users connecting in remotely.
No problems with performance whatsoever at this point.
Ok its not enterprisy its just a small business with 20 people but seems fine to me. I run synology servers.