Part 1, PREAMBLE:
In the Half-Life 2 leak, there is a file named hl2_scripts.dsp. hl2_scripts.dsp is file that offers a look at the scripts folder from an early point of development. Something of note is the mention of AI schedules, which is oddly in the scripts folder and as a separate .sch file (normally, NPC schedules are indicated directly within the source code)
In it are two AI schedule formats. one being "npc_[name].sch" and the other being "[name].sch". It can be infirred that [name].sch is older becaue of the reference "sacktick.sch". (Sackticks being a xen alien mentioned only in the Hyper era)
Now that we've deducted that [name] is older than npc_[name] we can deduce how old it is. The oldest map we have with NPCs is c1a3a_port from December 18, 2000. And, behold, the NPCs use npc_name. (npc_combine_s, for example.) This tells us that [name].sch is from before Mid-December, 2000. Now, there are few [name].sch references in hl2_scripts.dsp, but the few we do have are a bit odd.
For example; lead_monster.sch, proto_sniper.sch, sacktick.sch, and kungfu_owen.
Part 2, KUNG-FU OWEN:
Ok, so in the text above I have established two things about Kung-Fu Owen
1. Kung-Fu Owen is from 1999 or 2000 (Likely from Hyper era)
2. Kung-Fu Owen was an NPC.
That's all the concrete statements we can say, so know we can ask this one simple question: Who was Kung-Fu Owen?
We can say with some certaincy that he was Odell due to
this picture calling Odell "Owen".
We can also tell that he was to do martial arts, as he is called "Kung-Fu Owen" and not "Talk for a minute and 1/2 so you can then let the man you just met 5 seconds ago to do your work for you Owen".
However, that's the thing.
Premise 1: The statement "Owen is Odell" is true
Premise 2: The statement "Owen practices Kung-Fu" is also true.
Conclusion: The statement "Odell practices Kung-Fu" is therefore true.
Sound logic, but it's absurd. Odell, the Hyperborea engineer, is a Kung-Fu master?
However, I've got an answer. Odell's face texture wasn't always the one we know and love. In Odell's textures file, there is an old texture from 1999 of Odell's old face texture. Formatted in a Half-Life 1 style format. Odell's face texture from the leak was from a martial arts instructor. Kung-Fu is a martial art. So, Kung-Fu Owen was likely a test of Odell's face texture from this martial artist.
So, that's it. I spent 2 hours pondering this inquiry to only realise what it is while writing this post. I'm probably stupid.