Those oak pegs are just normal Armourers methods of reinforcing a heel or toe patch in the butt (or anywhere come to that.....). The pegs either side of the SCREW, front trigger guard have been inserted to stop a crack spreading from the front of the magazine well up, along the fore-end.
Where we detected a crack, we would spread the crack, squeeze glue into it, then insert the cross screw that you all refer to as 'the ishy screw'. In fact this was a modification formuated by Britain and is incorporated into our EMER's. BUT, it looked unsightly so instead of the screw, we started to insert an oak dowel..... or even a couple, depending on the apparent length of the crack. Hammer it in, leave to dry/cure for 24 hours and make good. It wouldn't crack again, believe me! And those undercut dovetailed and pegged butt patches will last a lifetime
From this Kar98, you can rightly assume that your rifle has been in Britishservice unless you find anything to the contrary
On the matter of the DCRA pins at the REAR of the fore-end, I could be wrong but surely they were there to reinforce the internal patches we used to call 'DRAWER PACHES', the hardwood replacement inserts used to DRAW the fore-end UPWARDS but REARWARDS against the butt socket. That as opposed to preventing the body moving left and right in the fore-end. It'd have to go some to overcome the centreing influence of the knox form/barrel reinforce