Where did you learn this? I've never heard this recommendation before and it sounds pretty out there.

Edit: it turns out that apparently both the American Dental Association and the National Health Service of the UK recommend not rinsing immediately after brushing. Huh, TIL.

Toothpaste instructions often tell you to rinse with a small amount of water, but dentists here always say not to.

And floss before brushing, so you can rinse goop out before the toothpaste goes in.

I'm flabbergasted

this is nonsense.

you're not suppose to eat/drink after brushing, esp anything acidic.

because you want the fluoride in the toothpaste to stay on your teeth. and it's like 10-15m.

you are suppose to rinse your mouth. just like you rinse the flouride treatment at the dentist.