Heat is just a lame excuse for poor work planning. Proper crews know how to manage their mortar with shade cloths and cool water. That lean sounds like a foundation or bracing problem they're trying to blame on the weather.
Yeah, that's just people blaming the tools instead of the hand using them, like @singh.jessica said. You see it everywhere now, from bad coffee to messed up brickwork. It's easier to point at one thing than admit the whole plan was weak from the start.
Wait, a whole brick course leaning? That's not just a little oops, that's a structural nightmare waiting to happen. The mortar setting fast would just make it worse, not cause the whole thing to lean like that.