None of that jives with any of my observations.
In my immediate circle alone - my sister is a strong extrovert and always has been. She thrives on large groups. If she's stressed and wants to relax she'll go to a party or downtown dance club or hang out with a dozen acquaintances. She's been that way since tween. I bring her up because she's very upfront, and I trust and believe her, that social engagements alone are NOT, and never have been, hard work or effort. They're natural to her, she gains energy from them, she enjoys them tremendously, and gets recharged through them. This is not my external observation but her convincing expression. I know others like that.
Then there's me :-). Lot of that, such as parties and dance clubs and even large groups of friends, sounds awful to me. Easy on assumptions though : As per my parallel comment, I've been a client-facing consultant for 20 years. I practice and teach soft skills and emotional intelligence at fairly high level at work. Having started as a hands-on techie for the first decade of my career, I haven't written a line of code since 2018 - ALL I do now is talk to and manage and coach and mentor people, meet with clients, etc. I spend about 7 hrs a day actively engaging people professionally.
And it's still as draining as it is rewarding and enjoyable. 20 years of active practice and daily high level socialization has not meaningfully moved the needle on whether I gain energy from people, like my sister always has, or drain energy even with people I enjoy doing activity I like.
Absolutely there's detail and granularity to this - I love teaching and have been a visiting professor for 3 years at local college. I love mentoring and coaching and do it daily. But at the end do the day I strongly crave alone time to recharge after social activities (which is what I call "being an introvert"), whereas I know people (I call them extrovert) who simply don't need that, at all. The notion that simply practice can change that, hasn't been the case for anybody I know.
You can gain skills and that's indeed worthwhile! But that does not automatically alter the energy management situation.
So my apologies, but your post is the most literal proof that some extroverts don't understand this, at all, and like Freud, make wild assumptions based on limited internal experience :-/. It's less of a capacity thing, which I'll agree may get expanded, and more of what does activity do and how does it draw on that capacity.