I need to agree with the author, with a caveat. He is a well developed developer. For somebody like him, churning out good quality code is probably easy.
Where i expect to see a lot of those metrics of feeling fast come from, is from people who may have less coding experience, and with AI are coding way above their level.
My brother in law asks for a nice product website, i just feed his business plan into a LLM, do some fine tuning on the results, and have a good looking website in a hour time. If i did it myself manually, just take me behind a barn as those jobs are so boring and take for ages. But i know that website design is a weakness of mine.
That is the power of LLMs. Turn out quick code, maybe offer some suggestion you did not think about, but ... it also eats time! Making your prompts so that the LLM understands, waiting for the result, ... waiting ... ok, now check the result, can you use it? O no, it did X, Y, Z wrong. Prompt again ... and again. And this is where your productivity goes to die.
So when you compare a pool of developer feedback, your going to get a broad "it helps a lot", "some", "is worse then my code", ... mix in with the prompting, result delays etc...
It gets even worse with Agent / Vibe coding, as you just tend to be waiting, 5, 10min for changed to be done. You need to review them, test them, ... o no, the LLM screwed something up again. O no, it removed 50% of my code. Hey, where did my comments go. And we are back to a loss of time.
LLMs are a tool... But after a lot of working with them, my opinion is to use them when needed but do not depend on them for everything. I sometimes look with cow eyes when people say they are coding so much with LLMs and spending 200, or more bucks per month.
They can be powerful tools, but i feel that some folks become so over dependent on them. And worst is my feeling that our juniors are going to be in a world of hurt, if their skills are more LLM monkey coding (or vibe coding), then actually understanding how to code (and the knowledge behind the actual programming languages and systems).