I’d need to double check mine to be sure, but I don’t remember it being on the speaker jack. And I seem to recall one of the changes on the last revision of the BE before the DLX was moving the NFB to the 4 Ω tap.
Here’s a post from Dave Friedman himself saying that moving NFB to 4 Ω was one of the changes:
https://www.rig-talk.com/forum/threads/friedman-be-mods.189660/post-2117216
There’s posts on facebook from him verifying the same, and that the Smallbox also moved to the 4 Ω tap in 2016.
Maybe whoever built yours slipped into old habits. The current gen BE100DLX has a 3 way response switch for NFB, so they’re all valid ultimately.
But yeah, one of my favourite aspects of Fractal is the ability to adjust the NFB. I do it all the time and love it. Marshall 1959HW is another one that has the NFB wire hooked up to the speaker jack “because it’s old school”.