Nope, a concession is no more binding than a candidate declaring themselves the winner.
They halfway did in 2000, hence the caution since then. They aren’t making a mistake this time: Biden won enough states that even if he ends up losing Georgia (which is very close) he will still win the Electoral College, so calling it by now makes sense. Biden could theoretically win Alaska, which counts very slowly, but Alaska is a Republican state: fortunately Biden does not need to rely on Alaska’s votes.