Recently I almost started a very similar topic, but my experience is that after thorough cleaning - soaking, scrubbing with soap and toothbrush, good rinsing, oiling afterward - the tools all develop a gritty phase and I have no idea why. It's the same no matter if it's a brand new SAK or an old one. And the grittiness moves around, wanders from one tool to another and after a while of opening-closing them it slowly disappears in the end.
It's a mystery to me. And really, I had this at least on a dozen SAK's.
(Okay, actually I have a theory, but no proof: as the toothbrush I use for scubbing was actually used to clean my teeth, maybe there are still some toothpaste particles left in it, but I can't see or feel any on my fingers, and it's been my tool cleaner brush for many years, it's been soaked and rinsed hundreds of times. And also undermining this is that in some cases I only used a nailbrush that never saw toothpaste, only soap.)