NUK teat sizes - totally confusing

[Bluemamma]

Hi all, I have 17 week old who has been using NUK bottles tear size M size he was 4 weeks. I read that it’s best to move up teat size every 2-3 months but NUK has only M and L. It’s says M is for 0-6 months and L is for 6-12 months. That makes zero sense, so a baby age 2 weeks and age 5 months eats from the same teat size M? What am I missing please? With my previous I used MAM and they had very clear teat sizes.

I’ve always used Nuk with my DD. She’s 20 months and still uses the 0-6 months M teat - I’ve found it really fast compared to other brands. I tried going up to 6-12 M and 0-6 L and they were way too fast. If he’s having no issues then I’d leave it.