Disclaimer: my formatting is never meant to be rude. I use it just as a functional tool to organize discussion and help reading.
So to paint and process the orders and ship 200 paintings takes him about a month
So, he does not produce 75 paintings a day.
Painting is not only... painting.
Watching him work in that last video, I think it takes more like 5minutes of actual painting per picture. Hes fast and like a machine.
No, he is not.
I saw the video you shared previously and, while he is certainly faster than me, he is not that fast. I can tell it by the movements he does with his hands, the pauses he does, etc...
Note that I can be quite fast (compared to many others). In 2016, I participated to a local 24 hour comic art challenge/convention.
I produced 4 comic book pages, in less than 8 hours: 3 in my style plus one in the style of another guy to help him to finish in time.
In the end
I was drained, and all I desired was to go to sleep or, at least, relax with a beer.
For reference,
the average production rate of a comic artist is around 1 page every 2 days or even less. And, in fact, the price of a comic book page (pencils plus ink) in USA is about $ 300 (I believe, I have already shared the link of Nick Macari, who explains it very clearly).
About the humble guy story
Even the personification of a humble guy could be a marketing strategy.
I am surprised that this is needed to be explicitly pointed out. Nearly nothing on Internet shows the true hard work needed to do something. We often see shorts of 30 to 90 seconds of artists painting (or drawing), often without even a construction sketch (

), and played at fast speed. That "show" that we consume in around a minute took actually even an entire day to plan, pre-produce, perform, edit and publish.
If he is truly humble and not promoting in that way his work, then they are the media that exaggerate about his performances.
Time and Quality/Detail
There is, of course, another variable to take into account. We all saw his paintings. I hope we all know that no one can paint the Monna Lisa in 9.8 minutes.