Yes, a few centimeters doesn't really matter for the airline, weight does because there are actual people who need to lift them. So they have zero incentive to measure and potentially conflict with a customer. This is very different from carry on which needs to fit in the bin or underseat. Don't push it , obviously: if you show up with an empty 30" cube then they will refuse you because it doesn't fit in some aircraft doors and they will have an easy time because you are at 90"...