Cannot use CIDR greater than /24 - WHY?

Why is the network discovery changing my CIDR from a /22 to a /24?
How can I override this?

You can‘t. The reason is that /22 has too much addresses to fit into memory during discovery. Originally we didn’t have any restriction and it led to out-of-memory errors.

And there is not a method to override this? Add multiple blocks for discovery, or similar?

Are there any plans for making this configurable?
1024 addresses should not take much memory and our control hosts are all configured w/ 32GB.
This is a deal breaker for the client, they have 4 sites each with mirrored networks, ~ 820 devices, and purposely keep the manufacturing lines on a flat network.

openHAB frankly makes a really poor network monitoring solution. You would be far better off using software specifically designed to do this job such as Nagios, Zabbix, etc. And openHAB is a home automation system. It lacks many features and capabilities that make it suitable for an industrial or manufacturing context.