Ever do a hard pull and have someone or something require that you clutch-in, cease and desist? I've done this before; RPMs start to fall but all of a sudden the ECU kicks in shoots the RPMs back up and holds it there for up-to a few seconds. It seems quite intentional and don't think they're just arbitrarily doing it. If you're going to disable it, I think you have to remember to keep the RPMs up, under that circumstance, as the ECU was programmed to do.
I think what you're describing is just the high friction point and small friction zone of the clutch. Shifting is all about timing and throttle attenuation. Add the fact that we're dumping boost with each release of the accelerator and can take longer to rebuild if letting the RPMs fall. Even though you're returning the accelerator pedal to the same or similar position, power levels can be wildly at the time of reengage. Personally I'm used to adjusting my shifting to the vehicle. If you're engaging quicker and at a higher RPM, you may have to use more or less throttle than are accustomed to with slower engagements. Since the gear is already engaged and are just waiting to release the clutch, it's not really the RPM fall we're waiting on, but instead on the power level to be at a more predictable level for smoother engagement.