"Best play" is a perfectly well-defined concept in game theoretic terms. I means it only contains moves with the optimum value, where the values are "win/draw/loss".
"Best practical play" is context-dependent, and a rather fuzzier concept, relying as it does on an implicit notion that the opponent makes errors stochastically.
There's no such thing as best play, except in situations where only one line achieves the desired, predictable result of a draw or a win. It simply doesn't exist other than that and if any experts have defined it wrongly, then they aren't very expert experts. In fact, they are quite mistaken experts.
guys?
Is this where you jump in to say "stop it now!!!"?
You need to be careful about that...you're going to become a meme like "Leave Brittany alone!!!".
You know that is part of France, right?