If one assumes that the two species are related, then 2-3 meters is a better range than 1.8-2 meters, per onscreen evidence.
What onscreen evidence you speak about?
The only onscreen evidence what I know of is that none of the shown Caitians was reaching even at least 2 meters.
There is evidence that Kzinti were tall to 3 meters as you shown, but not evidence of such large Caitians. Or is there?
The argument "Species_A and Species_B are related" is irrelevant for height of either of the species.
Look at this comparison chart of animal sizes. Notice the obvious difference in size between Lion, Cheetah and Jaguar. They are all felines having same roots, but it didn't prevent them to develop into different sizes. Especially notice that Cougar is about half size of Lion:
So IF one assumes that the two species (Caitians and Kzinti) are related, then there is still no way how to guess height of Caitians from Kzinti, or reason to claim that 2-3 meters are better.
(Caitians could be the Cougar and Kzinti could be the Lion from the example above).