It's certainly has nothing to do with security. It's Google's way to force you to use Google Analytics if you want to track said informarion.

Google Analytics does not give you additional keyword information.

If you want keyword information from Google search results, the best way to get it is actually buying ads for those keywords. And in fact some marketers allocate ad budget to keywords they already rank for, specifically for that purpose.

But to the grandparent's point, GA used to give you a ton more organic info at the keyword level. It is part of what drove the seo industry. The only way to get an abstract view of that keyword volume now, including on your brand terms, is to buy ads and run the organic reports.

Also, it prevents you from exfiltrating Google's ML model for search and build up your own.