1.02 patch notes say they made Kinetics lighter.  They used to weigh 28, then lighter and now lighter still.  All the same size is correct though, they always were.  The truth is they don't do crap for damage and have less than half the range of missiles, but you can buy a lot of them and they have an amazing rate of fire.

I certainly think the current mass is good for early-game kinetics. Late-game kinetics would be obscenely powerful at only 6 base mass. As it is now, Graviton Throwers are better than level 2 Durantium Drivers, and Singy Drivers are a whopping five times better. Normally, each increase in weapon level adds +1 to the mass cost, so if that follows, that means Singularity drivers will be 10 mass once they're done. I'm sure this is only a first test.

The xml files are compiled together for each new game, if you open an older save game it will be operating from a different set of parameters.