Act
Actually, if I recall correctly, you needed to have the "CA_GLIDEANDCLIMB" ability in order to do it before 2.2.9.
Even in the link provided, the ability has that description:
View attachment 44854
Now that 2.2.9 introduced the CANBUSTWALLS flag, I'd imagine they found the presence of that detail in the GLIDEANDCLIMB ability redundant, thus removing it. Any character that has the GLIDEANDCLIMB ability, but not the CANBUSTWALLS flag, would thus stop working properly in 2.2.9?