That's an interesting hypothesis, Jim C. However, my understanding is that the hole for the pawl spring and ball bearing was drilled through the oil hole, which would make failing to drill the oil hole implausible.
My understanding is based on reading that on several forums; a link to one is provided below (which seems particularly relevant here as will be discussed below).
The oil port may be only a secondary reason for that hole, the primary one being access to drill the pawl spring hole. (Reportedly, some other ratchet types (from Moore Drop Forging and other manufacturers) simply leave that hole, which was used for drilling the pawl spring hole, open rather than putting a ball/spring oil port there. I can't find a link to such reports at the moment, though, so a grain of salt would be appropriate.) The later, NonOH types must drill the hole at an angle, through the pawl/direction-switch opening (or the main drive gear/anvil opening). The link below includes a picture of an Easco NonOH ratchet demonstrating the angled hole drill for the pawl spring and an oil-hole 1/2" Craftsman one showing the coaxial oil hole and pawl spring hole (that would have been drilled through the oil hole). Presumably, the 43186 uses the angled-hole method, though I haven't taken one of mine apart and confirmed it. (Same would go for Type 10+ 3/8" and 1/2", though I have few of those, my collection focusing on 1/4" drive ratchets, which take up less space.)
Also interesting in the link below is that, for unknown reasons, some oil-hole generation ratchets had the hole plugged and chromed-over. There's an example (a 3/8" ratchet) pictured on the linked page and references to others.
I suspect that my NonOH 43175 has the same thing: a hidden plug inside, installed before chrome plating. I don't know why this was done, instead of keeping the oil hole. Maybe to save the cost of the oil port ball, spring, etc.
It's unknown how many of the 3/8 and 1/2 Type 10s actually have a plugged oil hole and how many have the pawl spring hole drilled at an angle instead. Disassembling several Type 10s and checking for the plug & straight hole or angled hole would be telling.
At some point, I'll disassemble my NonOH 43175 to see if it has the plug and straight hole or the angled hole. Either way, it's a 43175 without an oil hole whereas all the other 43175s I've seen (and all 43185s I've seen) have the oil hole. (It's up to you whether you call that a Type 10 or just an anomaly (of which we so far have only seen the one example).)
Here's the link I referenced above:
https://www.garagejournal.com/forum/threads/craftsman-ratchets-with-grease-fitting-in-the-head.55492/The use of a plug in the oil hole is discussed in posts #9, #10, and #14 (at least).
The angled pawl spring hole Easco is pictured in post #18.
The co-axial oil hole and pawl spring hole (as would have been drilled through the oil hole) is in post #23.
The 3/8" with plugged & chromed-over hole is pictured in post #32.
If you haven't read that 2010 thread before, I think you'll find it interesting. It has some overlap with your research and has some "questions" where you later provide answers.