Let me give an example of the usefulness of fine motor skills at online poker
My gaming mouse has 12 buttons on the side (I only use 7 of them so far). Sometimes I press a wrong button with my thumb: the minraising button instead of the one that raises to 2.5 bb. This loses some EV. Besides, I need to train my reflexes to 'remember' which button does what.
I'm only about as fast as a median online grinder, i.e. thrice slower than Dmitry, and can only play at 3 Spin & Go tables (often just 2), making decisions once in 3-4 seconds, but even so, I think I'd have to spend an extra second to locate the correct hotkey combo on the keyboard or to hover the mouse over the correct betting button at the table (hence 5 seconds per decision) if I didn't use the extra mouse buttons, and that would either lower my poker volume by 1.5 times or reduce the amount of information that my brain can realistically process when making decisions within the short timeframe.
Also, the highest undertitle for ordinary 2+2 posters is called Carpal Tunnel for a reason - it's a professional disease of those online grinders who neglect the physique instead of buying vertical mice. The sedentary lifestyle may also eventually lead to back problems. Even though the said issues are common in all those who work at the computer, they're especially probable in those who play long sessions without taking a walk.
I know that the above considerations are secondary to learning the strategy, just I wanted to present a view from the perspective of online poker where the finite speed of human cognition becomes the performance bottleneck once one grasps the strategy at an expert level and moves up to the high stakes.
I didn't mean to glorify 10-tabling - I actually think that, during bankroll building, a good rule of thumb is not to play at more tables than the average number of players at the table at the given poker format - but once the bankroll grows large and one's hourly winrate reaches a plateau because there are too few weak opponents at higher stakes, one faces a choice between improving the strategic knowledge even further and improving the multitabling ability, possibly dumbing down the thought process in order to handle more tables efficiently without sacrificing too much accuracy.
As much as you may dislike it, the latter option is often the low-hanging fruit because of the rapidly diminishing returns on the investment of time and effort into learning the strategy, and also because the hourly variance grows quadratically in the buy-in amount but only linearly in the table count.