You can argue that Smart went down very easily there despite the push. I'd then argue that Poole and GP2 each go down quite easily as well and it doesn't seem to hurt their whistle.
I think one of the biggest issues in how people view “flopping” is conflating at least three distinct, albeit overlapping, categories of behavior: (1) anticipating and moving with unavoidable contact (mostly a taking charge thing); (2) letting yourself get pushed/shoved instead of standing firm/resisting; and (3) taking a dive in the absence of contact or not logically connected to contact.
In my view the second category isn’t flopping, it’s just smart basketball that draws attention to illegal contact by the other team and is probably most of what Smart did on that Klay pushoff. The first category I also think is generally fine and desirable, not as a form of drawing calls but as a way to reduce severity of contact and injuries when players draw charges, which is a part of the game. There are probably occasional instances where the first category blends with the third, but I think it’s generally a lot closer to the second (resting more on your heels or even slightly leaning back into the fall ahead of contact). The third category is a problem, but is hard to isolate from the first two.
That said, people complain way way too much about flopping because it’s usually category 1/2 conduct, which there is nothing wrong with. There’s no rule that a player has to try to avoid the impact of a player on the other team shoving them. They can, and should, be entitled to either fight through and defend the action or let themselves get shoved down and try to draw a foul. And, as we all know well from the Bucks series, refs don’t necessarily call fouls unless you decide to let them impact you instead of playing through it, so if the league wants less category 2 behavior, they need to do a much better job calling contact when players do fight through it. Pretty much the only exception is offense at the rim, where this seems to be reversed and fighting through contact is more likely to lead to a call then letting yourself get pushed out of position.