M240L: 75-Round Mag Has Higher Mobility Than 50?

While testing the M240L, I noticed something that feels a bit odd and I’m not sure if it’s intentional or a stat oversight.

Right now, the 75-round magazine provides +4 mobility compared to the 50-round magazine.

From a logical standpoint, a 75-round mag should be heavier and bulkier than a 50-round mag, which would normally result in slightly reduced mobility.

Is this meant as a balancing trade-off for something else (recoil, handling, ADS), or could this be an unintended stat mismatch?