Your experts used lazy thinking.
Quite often, parents think a child is teething when it is just in a ‘fussy stage’ (the visible marker of cognitive development, which happens in stages, is fussiness… more on that in a moment). More often than not, these developmental stages are blamed on teething, diet (allergies, not enough milk, etc.). But the fussy stages are very orderly in arrival (you can estimate time of arrival and behavior patterns fairly accurately).
However, just because parents often blame teething for fussy stages doesn’t mean teething doesn’t make one cranky. Teething may be pretty much a non-event for some kids, but just because parents blame teething for every other form of fussiness doesn’t mean that tooth-specific reactions aren’t also real.
I can attest to this. I remember teething (I can remember back to about 6 months old). It itches. Sometimes intensely, and often below the gum so that you can’t reach it. It also aches for short spans of time, intermittently (I remember the sensation was the same when my wisdom teeth were coming in - they’d move, then stop, then move, then stop). And it hurts a bit, too, as the teeth come to the surface and cut through. I mostly remember molars and my canines. That urgency to bite and chew is like… well, I guess it qualifies as a physical compulsion - even if I didn’t want to bite something, I couldn’t help myself. I remember chewing one finger raw and chapped, learning to turn it sideways so that I was biting across the knuckle bend instead of down on it (which hurt a lot). I remember the sensory overload of rubbing my fingers on the sore patch of gum, over and over, until the sensation took on a rubbery feel. I can remember the squeaky feeling (can’t remember if it made a squeaky sound, though).
Part of my crankiness was the out-of-control feeling I got, that I couldn’t keep myself from doing things that made them hurt worse sometimes (like biting hard) it hurt, and it felt good at the same time (the way wiggling a loose tooth feels good), but even when I didn’t want to put my sore chapped fingers back in my mouth, I’d find them there. Kind of distressing, considering I was only just getting accustomed to the idea that I was in charge of my body’s movements in the first place. (Though honestly, I also knew that I wasn’t nearly as in charge as I wanted to be - very frustrating to know what you want your body to do and it won’t do it, it just can’t grip hard enough, or stay balanced enough, or be dexterous enough… If I had known how to swear, I’d have been swearing a blue streak, but instead I had to resort to crying in distress and frustration.)
Anyway, if the researchers would just find people who remember the experience, maybe they’d pick up some clues to where to look for more data. Not that my nearly 37-year-old memory qualifies as clinical data, but I sometimes wonder if the fact that most people can’t remember before 2 or 3 years old makes them kind of think that there IS nothing of value before then.
As for the fussy stages, there is one book available in the US that lists them explicitly. The book is based on decent science (but the style is a little fluffy, try to ignore that part), and people tell me over and over that their kids hit those stages like clockwork. The book is The Wonder Weeks by Plooij and … dang, forgot the other name. But you can find it at Amazon (etc.). The main point that parents seem to find useful is that when you are pulling out your hair with frustration, and saying I QUIT (whatever it was that you were doing, like breastfeeding, or responding when she cries, etc.), and are wondering who stole your baby and replaced it with this needy, whiney, crying, clingy monster, you’re about at the end of a stage. Wait about 1-2 weeks, and you’ll have a whole new baby on your hands, with new abilities and comprehension. Oh, and the other thing is that the fussiness appears to be reality-based. That is, they really ARE more scared than before, more confused, more frightened, etc. They aren’t making it up, manipulating you, etc. Again, I can remember those things happening, and it was like the world went from black and white to color, gravity started working for the first time ever, etc. HUGE amounts of re-organizing my reactions, understanding, and sense of self were required each time. Very upsetting.