My theory (FWIW)
At redline-WOT, the injectors are running pretty close to wide open. When the fuel cut occurs, all the injectors close, so fuel pressure soars. The RRFPR rapidly bleeds off fuel pressure to get back down to it's targetted fuel pressure. Meanwhile, the engine drops below redline, the injectors go wide open again... and now fuel pressure really sags. So you're getting the same injector pulsewidth, but for the first few injector events, you're getting less fuel. The RRFRP tries to build pressure back up to it's target, but Whammo, you hit the fuel cut again, and the process repeats.
Just a theory - no measurements to support this, and I'm running a stand-alone setup, so this doesn't really apply to me anyway. Just some thoughts.