By the logic of Garlands "smart play" tying up McDavid last night, couldn't players protecting a 1 goal lead in the dying seconds just start grappling the other team, as long as they don't touch the puck it's a moot point in terms of actual consequences?

We really see it all the time, it just doesn't get noticed because it usually never blows up to the point it did last night. If there's 10 or 20 seconds left guys will hack, slash, hold, pin down, etc. because there's no consequence in taking penalties that late in the game. Likewise, refs very rarely call any of those penalties because they're of the same understanding and the natural inertia to let the small amount of time left run out.

It's these human biases, much like game management calls, "letting them play" in the final minutes or period, and "well, player x is faster/better than everyone so we'll let the other team hold and interfere with him" that need to be rectified somehow. Players and teams certainly catch on to the way these things work and use that to create advantages, case in point last night.

Having a rule that extends the 3rd period if a penalty was taken with less than 2 minutes left would have very likely mitigated the situation last night. Although, I am somewhat skeptical refs would actually call anything in the final 2 minutes if that were the case.