Is there any advantage to glasbedding a stock if it already shoots 1/2" at 100yds?

bedding will help with movement due to weather by sealing the mortice, i would think.

I don't bed .223s that shoot sub moa without it.

To me, the primary advantage of glassing a barreled action to a stock is to get a low compliance fit, so during recoil the stock acts as part of the gun. Uneven wood to metal IS low compliance relative to .223 recoil forces. If the deflection of the fit during recoil is already less that .0001", glass bedding is not going to change accuracy measurably.

If it ain't broke, don't fix it.