Thanks to all for putting up with my neophyte questions of late.

This one is in regard to the one or two crossbolts I see in wood stocks.
My guess is they are there to keep the wood from splitting under recoil.

I've not seen them in synthetic stocks, whether the synthetic material is some sort of 'plastic', reinforced plastic, or a composite of fiberglass/graphite/kevlar.
My guess on this one is that these materials don't split like wood because of the properties of the material used.

Did I guess correctly?

When recoil lugs are added to a synthetic stock, they are molded right in the stock, and are not visible from the outside like on a wood stock where ebony plugs are generally used to cover the holes.