That's just due to Mods 2.0 changes.
Before that you had a much higher chance of rolling a good speed secondary. Now, all 4 secondary stats have an equal chance of upgrading when levelling mods.
Before the change, the secondary stats that showed up in beginning were guaranteed to level. So for instance, a blue mod would show two secondaries at level 1. These two were guaranteed to level when going to Mod level 12. Now all 4 stats have an equal chance, no matter what initial secondaries you see on the mod in the beginning on level 1.