There might be something in that.
If you went back 50 years to mid 70s people were still using terry squares and twin tubs. Disposables were available, but expensive and not very reliable (source my mum who used disposables for holidays). The twin tub was a top load machine with one side with a big agitator in the middle, where you washed, then you had to physically move stuff to the spinner side.
There was a massive incentive to get kids out of nappies. Put them on the potty as soon as they could sit up, see if you could catch a wee, save washing a nappy.
By mid 80s automatic washing machines were a thing, Disposables nappies were more reliable and more mums were returning to work after having kids. Maternity leave was only about 6 weeks!
They didn't have time to be standing faffing with a twin tub washing loads of nappies. Or plonking kids on potties.
Pampers also paid a pediatrician to spout nonsense about readiness for potty training.
Much of which still gets repeated.
Between both the return to work thing and disposables being more reliable and the Pampers pediatrician lots of potty training techniques have gone out of fashion.
Schools are reporting more kids turning up in nappies I think the HV and nurseries need to be putting out more information on potty training younger. Including getting them use to the potty when they are babies, 6mths sit them on it while you run a bath, and the sweet spot for training between 20 and 30 month's.
I did the potty thing with my oldest, mainly because he liked to poo 💩 in a clean nappy. It definitely makes a difference.
When I went to train my youngest he'd arch his back and refuse to sit on the potty. But battle of wills I still had him trained in 3 days.