It's always been like that. anything that follows the 1-3-5 format for REing is 20% from green to blue & 10% from blue to purple. The ones that are linear (hilts, barrels, mods, etc) are 20% from green to blue & 20% from blue to purple. Has nothing to do with being a sub or not.
Now the logic behind it is lacking. You'd think the items with more paths would have a greater chance of discovery but currently that isn't so.
Unfortunately, the linear ones (hilts, barrels, mods, etc) are all now 10% from blue to purple on the PTS.