Logic and gameplay should often go hand in hand, but I'm always willing to stretch logic to make smooth gameplay. Fall damage is just lame, especially with the metrics of Castlevania's jump arcs, especially double jumps, and so forth. Having to climb back up in itself is enough punishment for the player.
Logically I can understand if Alucard can survive a huge drop, like SotN caves. Richter is a bit more of a stretch but given the Belmont's super human strength and skill, you could stretch logic enough to say he just knows how to land and is strong enough to take the fall. I do think there should be another tier of "fall stun" where you stop longer after landing as a result. More of a "Damn! That stings!" pause, rather than a "I BROKE MY LEG!" incident.
As a counter example where fall damage works, the idea of fall damage in say Ocarina of Time makes more sense. Link jumps as high as a normal human, and primarily when running off edges. The idea that he cannot land from a high fall safely is fairly intuitive. However someone in Castlevania normally jumps about 16 times higher than Link, and lands fine every time. Not to mention double jumps, which would be about 24-26 times higher than Link can jump.
Belmonts are just so strong and skilled they know 'how to land' and have the fortitude to walk away from it without an issue. Just show that it was a harsh landing by giving an additional delay before they can start moving again, would be the best 'correction'. But honestly, it's not that big of a deal in my opinion.
Oh, and what about others? Any sort of mages have magic, that's the ultimate logical fixer. Alucard is a super powerful vampire. Grant was an acrobatics expert. Etc, etc, etc.