That "annoying protrusion" can come in real handy on some frames that require it. Usually low end frames, but when you need it you need it. For those not sure what I'm talking about, there is an expander plug on the Shimano mentioned that will fit larger holes in BB shells. Sometimes the plastic guide is riveted on and interferes with cartridge BBs. Removing the rivet leaves a hole larger than an M5 thread. I just put one on a bike yesterday or so. Had to sand down the protrusion a little for the cartridge BB. Used a shorter screw as well. I was thinking the alternative was to put a copper round the same size as the id of the BB shell and mig weld the hole up. I did not want to do that on the low end bike I was working on for multiple reasons. Luckily I found a guide with an expander plug in the parts bin. Now I know that Shimano makes one I'll need one for another bike. One could always cut off the protrusion, and drill out the hole if needed.