First a nitpick. That's not generally what the term projection fallacy means although your meaning is clear.

How not? I'm stating that he's assuming that the people of tomorrow/yesterday shared his same beliefs as to what "easily accessible" or "hard to reach" meant in the arena of oil production. In other words; he was saying that "hard to access" is a fixed point rather than simply being his current belief.

But there's a fundamental problem with this: even as the technology does get more expensive, the total amount of oil does go down,

No, that's not a fundamental problem. I wasn't pretending that my statement somehow abrogated the 2nd Law of Thermodynamics. When people talk about "Peak Oil" what they're talking about is a catastrophic scenario where the production of oil-related energy reaches a crescendo and declines at exactly or analogously similar rate to which it ramped up. THAT, and nothing else, is "Peak Oil".

Similarly, inflation adjusted price of oil has gone up over time.

Certainly, but that's just not a criticism of my position.

Coal does have its own problems.

Certainly. But those aren't problems, mainly, related to existential risks to civilization related to energy supply, so much as they are to moral quandaries related to specific choices of energy production.

Moreover, coal prices have also been going up faster than inflation.

I'm sure. Coal has stayed extremely cheap comparatively speaking. But it's also in a similar -- if far longer-term -- situation as oil; there's a fixed amount of it and we're getting better at harvesting it, so the supply will inevitably dwindle. That's why, furthermore, I mentioned torrefied lignocellulosics. With just a bit of tweaking and expertise, switchgrass can be grown at (potentially) as little as $15/ton. That, after torrefaction, makes it ball-parkish to coal.

Another viable criticism, by the way, of the F-T process is its environmental impact due to CO2 offgassing. (F-T has a large CO2 footprint).