It’s an interesting approach to analyze it, but there are some key oversimplifications he makes:
First, he states that all digital cameras use Bayer matrices and that there’s always a “lie factor”. However, if you use a monochrome camera and shoot three separate images with RGB backlights, you capture the true resolution of that sensor and thus you have no “lie factor”.
He also chooses only one film stock to calculate the overall film resolution. But the film stock he chose is on the higher end of photographic film stocks. Different film stocks are going to have more or less film resolution by a wide margin. The displacement of grains in the film itself also play a role. (If you have copies of copies of film prints, the true resolution will be significantly less.)
And there’s also dynamic range. Film cameras can have more dynamic range than some digital cameras, but by scanning the film at three different brightnesses and merging them via a tonemapping algorithm, one can get past this issue.
I recommended you take a look at this analysis; this person tests different film stocks and presents how different film stocks measure against digital cameras in both spatial resolution and dynamic range.
EDIT: I should also state that regardless, I do agree with you in that we should always keep our films for as long as possible. Mainly because they can sometimes last longer than their digital counterparts, and are useful for those continually upgrading their film scanners.