I'm not trying to relate this back to the AI/junior/senior developer question, I'm just curious about the dynamic in poker since you seem to know what you're talking about.
Another analogy that might work is chess. I’ve only ever played “classical” chess and when my son got interested in playing I would crush him every time. Up until the point he got into bullet chess and was literally grinding out dozens of games a day where I’d casually play a game of classical chess like once or twice a month. His confidence and ability skyrocketed and I’m not even a challenge for him anymore. Now I’m not a real chess player, and there are areas of his game that are definitely weak compared to classical chess players who have played as many games as he has. But to turn around so quickly from not being able to win a game against me to dominating me in every game was impressive.
There are definitely online players who lack the skills you're describing, but that's not as much of a problem as you think. You can hide tells just by shutting up and staying still while you're in the action.
The other half of that is reading other people's tells, and online poker is more helpful there than you'd think. Most of reading other people (especially at relatively low-mid levels) is about reading the story they're telling with their action rather than reading their face/words/etc.
Classic example is: There are two hearts on the board on the flop and the person calls your bet. Turn comes, not a heart, person calls again. River comes, not a heart, person suddenly bets big to try to get you to fold, because they had two hearts and failed to make their flush.
Bigger picture, you read their style of play. Are they playing a lot of hands or very few? Passive or very active? None of these things require reading the person's mannerisms, and you can practice all of them very well online (though online you also run tracking software that gives you stats on opponents, which helps when you're playing a bunch of tables at a time).
Writing this out makes me miss online poker. Shame the games are terrible now (and I also have a child and business as opposed to the endless free time of my twenties, to be fair).
For me, there was definitely a high level of anxiety and nerves when I sat down at a table for the first time again after playing online for a while. But it gets easier and easier to shake that off and just get into the flow of watching betting patterns (which is the main thing you have to work with online) which to me was always the primary source of tells rather than anything physical. So maybe in my case the answer to your question is yes haha :) though it didn't seem to impact me negatively much.
To put things bluntly: at any tournament, 90% of the players after the first round will be players who learned in-person. Only a handful of online players (like Moneymaker) have made a successful transition to professional poker.