I disagree with the author's premise that you have "grit" only when it can be applied in any direction. To me, "grit" requires adversity instead of simply overall breadth. It's quite easy for us humans to do something if everything is going well. What about when it's not going well? Do we have enough to persevere through all times, including hard ones? Your startup is failing? Your research is yielding no fruit? You…
There isn't a single thing on his list that counts as grit (based on my understanding) except perhaps in some circumstances programming and networking, even that's with the caveat of using those two as a means to escape poverty. Most of this list are "nice to haves" and grit doesn't really apply:
Running, Lifting weights, Writing, Sticking to a diet, Developing a wake-up/go-to-bed schedule, Mindfulness, Reading, Networking, Music (piano), Baking, Cooking, Programming.
Grit is when everything has gone wrong, you're hosed and overwhelmed and the stakes are crucial and you get out of bed and "get at it" anyway. If you have even middle class parents to go home to... eh, then grit is mostly replaced by capital and calculated risk.