I'm pretty sure the motorcycle, stoplight, and bicycle ones all are deeply flawed. I regularly select all of them to the best of my judgement and it's like NOPE!
I feel like it’s not quite 50/50, more like 90/10 instead.
90% of the people didn’t care or look close enough. The Captcha algorithm picked that up. The remaining 10% of people who actually use their brain have to either gamble on that 10% chance, or succumb to the hive mind to save that 3 seconds of their lives.
I got one yesterday that was like, "Identify all the pictures with busses." and I swear to god, they were all just static. I just clicked continue and it was like, "No... There are definitely busses here."