The clear distinction is a thing that much postdates RQ3.There is, however, a HUGE problem with large unbounded skill lists. They are just unworkable. I'll use a character sheet from my long ago 80's CoC campaign that I dug out as an example (I will also note, I was wrong, this is CoC 3rd Edition, still really old):
There are 72 skills on the character sheet, and the list is 'open' (there is some space to add more). Weapon skills are not listed either, you have to write those in (presumably there are potentially a vast array of them). The character in question seems to have 10 skills with a rating, so she will be baseline in all the others, meaning she has anywhere from a 0% rating up to 25% depending on the skill. Of the 10 she's got points in, 5 are at or below 30%, and 2 are at or above 60%. She's a 'parapsychologist', which IIRC is a specific occupation or at least a variation of 'academic', yet her psychology skill is only 35%. So, frankly, this character has few really usable skills, library use and read/write (English) are the best.
Now, suppose she has to conceal herself, what skill does she use? Well, there is Camouflage, with 25% (the base level, we are all able to sort of do this), BUT there is also Hide at 10% (again, base level). Which would apply? Some situations might seem to mandate Hide, but MANY could be either one, flip a coin! Why do we need Camouflage? Why are people so much naturally better at it than 'hiding'? There is also 'Sneak' which has a baseline of 10% as well, but if you are sneaky shouldn't hiding and sneaking be pretty much correlated? One is unlikely to achieve great ability in one and not the other for sure...
Likewise we have Debate, Oratory, and Fast Talk. Why do we need all of these? I mean, sure, I can kinda parse some difference between them, but MANY times you will simply want to 'talk' and now you have to pick from several skills, and you may have drastically different ability to employ these often subtle variations. Nor would I limit the world to these 3 realistically, there are certainly many other variations of human communication at that level of granularity! Nor is it clear why you would use these instead of other skills like Law, Psychology, Speak, etc. depending on the situation. Since CoC doesn't clearly distinguish whether intent or action is the relevant factor we can VERY OFTEN have many choices.
The examples make it clear you test on the method, not the goal, (I know RQ3 better than RQ1)
In fact, almost every game pre-1995 (every one I've seen) has only implied outcome by stated method. And, since the method is what is tested, the GM is (in most cases, explicitly) expected to decide the coucome based upon the stated method.
"I waste him with my crossbow!" is, in RQ, pretty damned clear in intent. And explicit in method. Shoot him.
"I shoot him in the Eye" is implied intent and incomplete method - while the games didn't usually ask intent, many GMs would... "Shooting to blind or to kill by hitting the weak braincase behind the eye?" thus allowing the adjudication, and the missing element of the method being which weapon can (and usually was) inferred from what's ready.
As for "Broadly incompetent" - that entirely depends upon the GM and their rules knowledge. Let me rummage for the book. Got it.
Lookign through the skills chapter, the default assumptions include no extra tools other than the absolute minimum to do the job, some time pressure (except boating) Neither perfect nor horrible conditions.
Many GMs didn't read these elements out of the text... likewise, the transport skills are to get it moving; only significant speed, or tricky maneuvers, require a second roll.
Heck, ride is explicit that riding a riding-trained horse at a walk, even for a long distance, is no roll. Your ride check is your chance to do a novel behavior or to stay on when the horse tries to shed you, or is running. (Horse walk speed is about correct for a tolt or canter.
I've worked with horses a small bit. Well trained, cooperative, friendly horses of the Icelandic breed (both registered). I was able to get to a full gallop... but the horse was helping.
Most GMs of RQ3 call for rolls too often, and without modifiers for beneficial circumstances. That percentage is for pressured situations, adjust accordingly.