Earlier quoted context omitted.
The concept of "weakly solved" is not original to this effort. IIRC checkers was weakly solved for years but is now strongly solved.
And you can go further Heads Up (ie two player) Limit (ie you decide to raise or not, the size of the raise is fixed) Texas Hold 'Em (the style of Poker most played today) is essentially weakly solved. The process used generates a statistical approximation and tells you how close it is to correct, in theory a perfect solution would beat this by that amount, in practice of course Poker is a game of chance, and so over…
You have a ~10% chance over 100k hands to be Professional players do actually get in statistically significant sample sizes, but for amateur players, most don't get enough hands to really understand their skill level.