I've seen A LOT of posts about making HP with a 318-So why is it so ???

I don’t think I’ve ever seen a n/a build, that retained the stock stroke, have a 30%+ increase in tq over the factory “gross” ratings, especially if you rule out the use of exotic heads.
Again, we’re talking about traditional platforms, without computer controlled engine management and/or variable cam timing.

Some examples of what you’d be seeing at 30% above factory gross ratings:

340 - 340 up to 442
383 - 425 up to 552
440 - 480 up to 624
440-6 - 490 up to 637
426 hemi - 490 up to 637