In addition to the vibrissae explanation, I also wonder if their eyes (vertical pupils) just see better when it comes to height and not width, necessitating greater hesitation when it comes to judging things at their height and not high in the air. I am thinking they might need to move their head or eyes a bit side to side, though it may still be too fast to be readily apparent to the researcher. Relevant article [1]:

"If you have a vertical slit, you're very likely to be an ambush predator," says Banks. That's the kind of animal who lies in wait and then leaps out to kill. He says these predators need to accurately judge the distance to their prey, and the vertical slit has optical features that make it ideal for that.

But that rule only holds if the animal is short, so its eyes aren't too high off the ground, Sprague says."

Ergo, cats have vertical pupils but tigers have round pupils. The tiger can probably judge horizontal distances better than the cat.

1 - https://www.npr.org/sections/health-shots/2015/08/07/4301496...