He actually was super serious.
FRM is meant to go with transparent paint and if you put a block of wood where the tremolo should go, it'll just look fugly
To answer your question tho, it works just like it's supposed to work. Can be done 2 ways tho, filling a bigger route and putting a block of wood in there permanently, or making a little "fill in" like Paul has on some of his PGMs that can be taken out.