Are you sure you're not thinking of multi-tap on a keypad and not T9?
Once you've learned T9 (the one where you tap a key a single time for each letter in the word and a lookup is made based on the combination). You can surely be faster than Qwerty.
This was also the reason I developed https://typenineapp.com [1] for iPhone once they allowed custom keyboards.
I am on average 20wpm faster (50wpm for english, 60wpm for my native language danish) with Type Nine on my iPhone compared to the apple qwerty keyboard.
Even though you don't have the tactile feedback of the previous T9 phones on the iPhone I can type without looking just the same way as on a phone with a physical keyboard.
[1] More on my thoughts here - https://medium.com/porsager/a-better-iphone-typing-experienc...