Placebo probably. Unless you screwed up your other config somehow.
#how does mastercomfig get better rockets than other configs?
naive ibex
deep delta
Low-level:
It looks like Mastercomfig has three sets of network settings that it uses for different classes: net_hitscan, net_projectiles, and net_spy.
By default with mastercomfig, Soldier uses net_projectiles, which does a few things. For example, I see that it sets cl_interp_ratio 1, and uses the mastercomfig defined interp_low settings.
My guess is that this net_projectiles setting could be a big part of the difference you're describing. There could be other differences that play into it, too.
High-level:
As far as I know, no other config project has invested the same time and effort into researching and testing the config setups as Mastercomfig. The dev team treats it with a level of seriousness and professionalism that's stunning for a community project.
This is probably an oversimplification, but in my mind, I think of Mastercomfig as the successor of configs like Comanglia. (The last I saw, the newest version of Comanglia was a fork of Mastercomfig.)
If the rockets actually are more responsive using Mastercomfig, it's because of the time and effort they invested into researching and testing everything.
naive ibex
No, it's literally just the low interp on soldier (net_projectiles), which any decent config SHOULD have.