Hi, I'm a huge Rick fan (even met him and got an autograph once), and I'd like to invest in one of his carry-ons: either 21" x 13½" x 9" (including wheels), 6.5 lbs. or 21.75" x 14" x 10” with wheels, 6.7 lbs. I’ve taken no international flights in 27 years. This fall I'll be flying Vienna-Zagreb on Croatia Air, whose site says: 21.45" x 15.6" x 7.8" = 44.85 linear ins. are allowed dimensions. Can their requirements be so stringent that even Rick's int'l luggage’s dimensions are unacceptable?
Croatia Airlines' website says that the max size of hand luggage is 55x40x20 cm. That probably means that the maximum size is 55x40x20 cm, and if your bag is bigger than that it is not allowed as hand luggage. They aren't really flying A380s on the route, so cabin space is limited.
Or you can take the train, it's 6:30 by direct train.
In answer to the last question, Yes. Most of the world hasn't heard of Rick Steves and he never strives to comply to every nuance.
The challenge I see is the depth of his bags. Neither will fit into an airport suitcase test frame.
To be honest, that depth measurement is going to be a challenge for most North American suitcases. Why not just check it.