When I've run it, it becomes a simple process of putting a pair of fighters with plate and shield (or chain and shield if you go after the kobolds first) into a 10' wide corridor (or better yet a doorway), such that no more than a couple of kobolds can face the party at a time, and then regardless of how many attacks they are facing, the kobold need nearly a 20 to hit the party, while the party can rather easily hit the kobolds in return and generally lethally if they do. Also, remember, we generally started with a large party of 8-12 characters (2 per player), plus henchmen, dogs, and men-at-arms hirelings. So, yeah, you can win those fights with even low level characters, but they are a nightmare of tedium to go through because its just dice grindy at that point.
And it doesn't really let up. Pretty much every fight in the whole module is like that. There is a fight with 20 skeletons and 20 zombies as pretty much the climax of the adventure in the Temple.
This is pretty typical of Gygax, in that Gygax is expecting 12 players who are all former wargamers at his table, and thinking of D&D in part as a tactical wargame generation device. You see the same thing in the G series and the same thing in the WG4 and the same thing with the bandits in the moat house in T1, with a mass combat being a big part of the game, and the players expected to adopt hit and run commando tactics, make generous use of flaming oil, and to wear down the foes by fleeing and returning multiple times if needed.
And for me, the real problem here is even if you are claiming maps and stat blocks and encounters are the really valuable part of a module, and the really hard part of a module, the problem is that none of this stuff is really even that good, either by the standards of the day or Gygax's own best work. I enjoyed it as a kid, but only in the same way that I can remember playing the card game 'war' as a kid. Monotony meant different things to me then.
And back to the incoherence part of it, in the worst of Gygax designs what you see is that the stronghold of the monsters is more or less entirely working against them. Those 10' wide corridors and guard rooms that the monsters defend are their own death trap. If they just sallied forth from their lair and surrounded the party on open ground, they'd probably win. In the same way, if the frost giants in the glacier rift, just sallied forth from their glacier rift, they'd easily overwhelm the PC party. But Gygax is designing the terrain so that if the PC's fight it in the intended manner with the monsters being stupid, then with "clever play" like making use of chokepoints and doorways, then the valiant party will get through it.