I have two T-8 and all with the same problem.
One was confirmed during use and the other was confirmed when it was new.
Does your US have the same problem?
I examined my universal support bars. Three have clean metal and one has a small amount of discoloration. At this point I should admit that I never use the stops for the square edge jigs, so I have never examined the threads at the end of the US.
Since this bothers you, I would suggest using a small bore pistol copper brush to clean the threads. I would follow this with some rust preventative on the screw run in and out a couple times and left out.
Ken