Yep, it would be readily apparent by that point. You wouldn't even need to "solve" it first; you would see pretty much instantly that the last layer was in an impossible position.
Source: I got into speedcubing for a couple years in high school and averaged in the 30s, with a record of 26 seconds.
This is absolutely true. I believe he was at least using ZLL at that time, so it only took him 10-15 seconds to figure it out.