You're missing the point. Look at my lead sentence, the plank does activate 100% of your abs. The science is there, the plank is an ab exercise. It’s just a bad one, with clear alternatives.
My conclusion came from athletic trainers Martin Rooney and Jeff Cavalier who are cited in this article. Along with that, I cited the most popular ab-workout programs on YouTube (which feature no planks).
Yes, there is no blow the door open study that reveals the plank is the worst exercise ever engineered. But if you study athletes and people with real core strength (such as the two trainers I mentioned who have millions of followers for their ab videos) you will not see them promote the plank.
But if the plank works for you, keep it going! The record is over 8 hours long now from what I’ve read.
Lastly to address the Harvard article you linked, where the author writes “it is often the longest and most grueling 60 seconds of my life.”
If holding a plank for 60 seconds makes you “sweat, shake and collapse in relief,” it reveals to me you have a weak core. That first paragraph of the article encapsulates everything wrong with the plank.
This is a publication about health and fitness, so if the plank works for you then continue to have at it. But know that you’re leaving potential on the table for a stationary, immobile and outdated exercise.