Almost all the U.S. domestic airlines specify 22 x 14 x 9, or 45 inches linear, with a few exceptions. According to the Kata specs, 22 x 13 x 8 are the internal dimensions of the main compartment. Does the outside dimension shown include the trolley? So you're saying it can be squashed down to basically allow shoehorning into the 22 x 14 x 9 box?

The link below lists most U.S. airlines. The info shown is not always correct, but it includes a convenient link to the carry on baggage policy for each airline, which does have the current carry on size and weight limits.

Airplane Carry On Rules by Luggage Online

I've just measured mine, with a PMW-350 inside, but VF removed so basically in its collapsed state the external dimensions are 22" (and a tiny bit) x 14" x 9", so it is regulation size with the trolley removed. I have had it in a British Airways size checker, it was a tight fit but it went in.

That's good enough for me. I'm ordering it now.