This may be true but obviously, in sport more generally, there are many instances of great older coaches who couldn't do half of what their players can do, and in some instances were never as good as their players even when they were young.
"dispelling a common leadership myth: that you should lead by example.”
Setting expectations is obviously important, but the article does nothing explain how this was done. For example do they use OKRs at Dropbox? Overall I'm disappointed that so many people have "waved" (liked) the post on Medium and feel like it deserves a counter-article to set the record straight.
The author agrees with you in that you should actually do the work (you're a tech lead not a PM or purely management) but also actually tell your team what is expected and enforce it, not just assume they'll see what you're doing and copy it.
We cannot expect people we are attempting to lead/coach to do a task if we do not demonstrate that we know how to do it. It's like having a personal trainer who is a couch potato, it simply makes no sense!
I really hope that other "tech leads" are not following this example! Put in the hours you expect others to work. Document your work the way expect others to. Write tested, maintainable & performant code as you wish others to. This is all leading by example!