Interesting. I had music theory classes back in the 70s and I don’t remember anything like that. Not doubting you, I just don’t remember it being taught.
Did I miss something, or is this relatively new…
The harmonics part I remember. I don’t remember the rhythm part.
I don’t think this is anything new, it’s just not usually the focus of any music theory classes, as it is more of an interesting scientific fact and not quite so useful if you are learning composition or trying to analyze music. It’s the kind of thing you learn when you start to get down to the nitty gritty and look at the physical mechanics of music at the level of sounds waves and wave harmonics.
Here’s a page where someone took different rhythms and sped them up until you can hear the intervals they are equivalent to:
https://dantepfer.com/blog/?p=277