Why did they reduce the number of bullets added to the magazine with extended mags? The K-Volt went from 65-58 the feline went from 55-52 the Scarab went from 50-46 and the machine pistol went from 40-30. What caused this change? And no post about it?

It's because of inflation. The price of the metal making the bullets has gone up, so that's where world economics comes in.