This issue has puzzled us for years, and maybe someone can help us out. :-)
When our first cat was an only child, she used the litter box without any drama or fuss. But when we got our second cat, Cat #1 stopped covering her feces and urine. We had four litter boxes at the time with clumping litter, so we had more than the recommended 'one box for each cat plus one' thing addressed. We were told that was probably her way of telling Cat #2, "Look, I was here first, I'm top cat, and you better learn your place in the pecking order, etc."
Well, Cat #2 didn't exactly appreciate that, and she'd go bury Cat #1's feces and/or urine and meow at the top of her lungs the whole time she was covering it up and slinging litter all over the place. Then not too long after that, Cat #2 started meowing before and after every time she used the litter box, but never during. Sort of like, "Hey, watch this! This is the way it's supposed to be done, you moron."
Okily-dokily. Fast forward about thirty years, and every cat we've had since then meows up a storm before and after using the litter box. The funny thing is that they don't do that when they first get here. It's like a learned behavior they pick up within the first couple of weeks or so, where Cat #2 tutors Cat #3 to do that, then Cat #3 tutors #4, and so on -- like some kind of bizarre legacy that's passed on from one generation to the next.
On the bright side, I always know when the litter box needs to be cleaned. ;-)
At this point, we're pretty used to all the noise, and physical issues have been ruled out.
We're just curious. Has anyone else ever had this problem, or have a better idea of what might be going on? Or do we just have weird cats? ;-)