I use an MC-462A on my KT7 non-A board and the holes are not plated through, nor have a ground ring around plated to them. I do not know about the KT7A, but I'd bet it is the same board with some different chips only. The fact that the board might have ground rings around the hole has nothing to do with them being grounded. The concern is that the added height they might contribute to the surface around the hole would keep the HS base from seating, with adequate force on the core if you use the shoulder washers. I used the shoulder washers, set the base and then removed it to inspect the distribution of the AS and it had been squished uniformly. If you intend to take the base off more than once or twice, I highly recommend setting the stand-offs and their nuts with super glue. The first time, I didn't and wound up with one spinning on me.
Hoot