I was specifying which dimensions that Pyramid Plunder urns should not generate in within the config file because i have a couple modded dimensions in my modpack. After saving the config and relaunching the server, the config file reverted back to the default black listed dimensions of the nether and the end. I am using the dimension ids and not the dimension numerical value.

It appears the mod may be regenerating the default config when the server launches instead of accessing the current config available on the server. That's just my guess since that's the only real way i can see the black list reverting to it's original settings. This is on 1.15.2