Um, I immediately got the Beholder reference the first time I heard it back in '79. It's a pretty clear reference, IMO.
I guess you are missing my point.
Given both the description of the Beholder and the name, sure you could get that reference.
Just given the name, sorry. I don't believe that your DM said "The farmer tells you he saw a Beholder" and your first thought was *Wow, Eye of the Beholder, that must be a floating round bowling ball with eyestalks coming out of it*.
I do not think that anyone could go from the name to the description, even if they thought of the reference.
One could go from the name (Beholder) and the description (floating round bowling ball with eyestalks coming out of it), to the reference (eye of the beholder). But that is not we are talking about here. We are talking about (just like with Rendclaw Fury), just having the name and being able to intuit something substantial from it.
All we have from Rendclaw Fury is the name which has no type of reference other than claws and fury. It could be like the Tasmanian Devil (cartoon version), whirling around with sharp little claws. But, it might be something totally different. The name is not sufficient, just like the name Beholder is not sufficient.
A "Hellbear" is some sort of scary-ass bear. When I have to describe it to a player on the fly, at least I have a decent chance of remembering what it is, as opposed to "uh, it's got some claws."
Yup. And if I use the name HellTroll or HellOrc or any name where a part of it is a known creature in D&D, we can pretty much assume scary-ass troll or orc or whatever.
The problem is when the creature has nothing to do with a bear, or a dog, or a troll, or an orc, or some other well known D&D creature.
At that point, it gets a brand new name and people often cannot use it to go from name to reference to even partial description because we have no frame of reference for it.
But, how is WotC supposed to introduce new totally different and unique unknown creatures without using brand new names that do not have known references? According to your preference, they should not do that.
Personally, I am totally ok with brand new names that have nothing to do with anything I have encountered in the past. I'll remember the names of the creatures which are memorable in my game and forget those that are not.