I've had the tt500s for 25 years
And Never had a cam bearing seize yet . would be a lot out there with diffrent non matching covers ,
Like some of mine . Can't see why it would seize .
I had dramas with non bearing cam heads where the covers and heads were not matched and when they were tighten down the cam would not spin , because of diffrent clearance .
plasty gauge is a good tool, back in the good old days with no money, a mortgage etc, cam rattling its head off, on the old Honda SL125 everyday to work ride,
surface ground the rocker cover down, figure 8's on wet and dry, plasty gauge check, rub some more, she's good to go, a new cam chain, Aviation sealant, the old SL ran for years, with only advance retard rattle in the points cover.
oh yer ended up cracking the piston in half whilst monoing in 2nd gear
loss of power, smoke out the back, rode it home, wacked a piston in it and was happy except for end float in the crank shaft