Man. this question went all day and no one answered him......you guys are slipping here on a holiday.
Answer: Because....
Ok, open all the blades and look at the inside liners. On the black sawcut you will see some circles of black plastic. These are a sort of large plastic 'rivet' that holds the scale in place. These sawcut scales are moulded or cast onto the liner/bolster and some plastic extends thru those liner holes and is smashed down making the 'rivet' head like spot. This is done before the knife is assembled so the spring rivet and blade pins hold the knife together, hence the spring rivet goes down as one of the last assembly steps. In the yellow, Dymondwood dark and Chairman red versions, the assembly process is different and the liner and springs are assembled with the blade pins and spring rivets before the scales are put on. Look down in the open knife and you can see that the liners are made to work with all the scale types, the three newer versions don't have the big hole milled out for plastic tabs because the scales (Dymondwood) are riveted on. I think I have a photo that will show the inside blade well for those that don't have a 300 series. But , in reality they likely don't care anyway....LOL 300Bucks
This is a liner just before the introduction of the new version 300s. But it lets you see the scale material that is melted in the 'rivet' head that holds the scale to the liner. These scales , I am dredging up weak brain cells here, are injection moulded onto the liner/bolster. A photo of the new versions will have more larger indentions visible on the inside of the liner in the blade well. I will look for photo or maybe even take one here in a minute.....
Ok, minute is up...here is the inside of the modern 300 blade wells. Lots of stamped indentions which can be milled out depending on knife version. BUT, all liners are not same, there are two versions. A front and a back, one skips a stamped indention, underneath the knife, bolt and hammer sheild on the black sawcut and the blue buck shield on the new ones. The back liner has more 'divots'. Any more teche and you will have to call Buck.