FullThrottle83 as confirmed on Discord, the odd "beta"/vulnerable results were because Cloudflare Rocket Loader interfered with my version detection code.
I have published an update to the lab that fixes the version detection and shows a message at the top of the scan if Cloudflare Rocket Loader was detected. Most of the features work but the list of extensions on the Lab will be incomplete when Rocket Loader is active, because my code only looks for specific patterns in the assets and those are different when Rocket Loader is active.
While Rocket Loader causes issues with my Lab scanner, I am not aware of it causing any issue when it comes to using Flarum. I am curious whether it brings any benefits though, because according to the Cloudflare documentation this feature accelerates the website rendering by prioritizing text and images and delaying javascript. But since Flarum is a single page app, nothing will be visible until javascript is loaded anyway. So it could maybe even be worse? I'd be curious to know if anyone made tests to compare the performance with any without Rocket Loader.