Yeah, the lower left control is weird due to the LED, and the size/shape of the hole in the plate is smaller than normal. I don't think they can make a silenced version of it, since there's no place on the plunger to put the padding.
By desoldering the LED and using some creative filing, you can replace it with a "normal" slider (when I silenced an 87U, I swapped the annoying slider with the one from the pause key, so that thee left control would be as quiet as the rest of the keys).