He has a significantly smaller chance to stop the Tedesco try than the Crichton try, purely based on vicinity and speed. Tedesco was at full speed, the best Boyd could've done is put in some effort to make the goal kick a little bit more difficult, but again, didn't put in the effort, would rather hands up and complain.
The Crichton try, he had a very realistic chance to stop, or at least decrease the likelihood of him scoring. If he changed direction marginally faster he was well within reach to help stop him, or at least try to. Crichton already had multiple players on him slowing him down, unlike the Tedesco example.
At this point in time Darius has stopped his run and has squared up to being in line with Crichton, if you're telling me he is physically incapable of now moving to his right in the space of the next 0.5-1.25 seconds, you're the stupidest person on here.
I'm not joking when I say this is where Darius ended up after the try is scored, he does not move a single inch from the position he's in, in the above screen capture.