The message you’re reading applies to the checkbox above for encryption, not the preferences url. The preferences key only needs to be set if you want to encrypt the configuration URL, it doesn’t affect what OP wants to do.
My memory is a bit fuzzy because I switched to Searxng after playing with Whoogle briefly, but I thought Whoogle stored preferences in a cookie or something similar; the preferences URL is for when you want to transfer the preferences for your current machine to another. So OP is misunderstanding what it’s for.
OP: if your preferences aren’t sticking, are you maybe blocking cookies entirely or something? I’m pretty sure you shouldn’t need to do anything with the preferences URL for your preferences to stick if everything is set up correctly, it’s only for transferring your preferences to another machine.
I mean the original lawsuit was for aggressively bundling Internet Explorer and kneecapping other browsers. Which sure sounds a lot like a minor variation on what they’ve been doing with Edge and Bing for a while now, without consequences. Antitrust enforcement is not something I have a lot of confidence in for the foreseeable future.