The post is essentially trying to give people courage to speak the truth (as you say).
You say "There is probably something wrong there if you treat social interactions with too much importance."
The post describes what's wrong. And it also tells you how to treat social interactions with less importance... by analyzing what you feel and why you feel that way... as you said.
You mention "successes and failures" and say that it depends on this "fixed mindset" vs "growth mindset" stuff. And here you imply the same thing:
"With a growth mindset, every social interaction is an opportunity to improve. Saying something awkward is simply an indication that you need to put more effort into that area."
So, if you are trying to "improve", it must be improving at something, which makes it into a game. Saying something awkward in itself shouldn't be considered bad or wrong.
You never mentioned the other people in the social situations once in your article. Isn't that actually the most important thing? What if, for example, they're assholes? What if you just don't get along with them? Is it a failure that you aren't compatible with them?
It's like you are trying to create and improve upon some sort of mask in order to fool people that you are someone you're not. If you are able to do so, not say "awkward" things, as you wrote, then you have succeeded (and also if you have a "growth mindset" you can learn to "succeed" more often which is a vast oversimplification of the mind and damn silly as well). Otherwise, you failed, and you need to "put more effort into that area". Reevaluate what you did, basically, so you can improve your mask.
It's ridiculous, and it is a game mindset.
If you want to connect with people, which is what most social situations are about, you have to start being honest. Concentrate on what's important, which for most social situations is having fun, finding something you enjoy, and letting your mind run with that. Not be in this mental deathgrip of constant thought of self-improvement and self-evaluation that you're espousing.