It’s not as clever as the author hoped.
I would say Ruby on Rails was a 10x on raw PHP in terms of feature specs per hour and AI is a 10x on Ruby on Rails (and its derivatives).
We're probably 100x the developer productivity on a per developer basis from the early days of Web 2.0 with PHP, just a personal anecdote though.
Why? It is a perfectly legitimate question where the answer is some sort of a percentage.
Who wrote the essay and in which percentage?