I've seen some people on Twitter say it was just a rope with a handle tied on it to pull the garage door down.
That makes more sense to me.
I couldn't find any images of the noose in question, a noose is tied a pretty specific way. I'd really like to see a picture because I have a feeling the guy was probably on edge with everything going on and just saw something that he thought was a noose and reacted.
Here's a pic I found on r/nascar - https://i.redd.it/wyw3rsz4zo651.jpg
Apparently, according to wikipedia and the wokerati a noose is any kind of loop on the end of a rope, not a specific type of slip knot designed to strangle or break a neck. Like many things, a common term with a well understood meaning has magically been expanded to mean almost anything so that they can now exclaim a broader variety of offenses.
Someone posted a pic on twitter of garage #4 and a garage (#5)? next to it. It wasn't close but you could see a similar rope hanging in both garages, both on the left side. I didn't save the pic.
Followup: FBI says rope had been in Talladega garage since October; Bubba Wallace not victim of hate crime - https://www.espn.com/racing/nascar/story/_/id/29354447/fbi-says-rope-had-talladega-garage-last-fall-bubba-wallace-not-victim-hate-crime