See? Generally - those rules that came with a commercial bator WORK for the largest percentage of people, in the largest percentage of hatching situations.
That's why they're instructions with the incubator and written rules on websites and in books. Because MOST people will have decent or good hatches IN THAT RANGE.
Then there are the people for whom the rules did NOT work. Their bator, or their house, or their altitude or their microclimate demands a different set of "house rules." And you only develop those with practice and attention.
At my house the rules kill a hatch every time - I can get about 30% to hatch if I follow the rules like religion which is flat icky.
Now I dry hatch and here it works. I rarely worry about humidity at all.
The bad news is you don't live in someone else's house, microclimate, altitude and you don't have their incubator.
So you get to follow the rules until you find out what works and what doesn't. You tweak in small steps until you get what you want. Clean, easy hatches of most or all the eggs that developed.
Hatching is NOT a science - it's part art and part nature, part miracle. Or they'd call it Chickening. Like fishing is NOT catching.
You don't get to count your chickens until they're hatched, dry, standing, walking and eating and drinking.
This happened to a relative of mine, also. It blew up all in his face.
I had one that cracked open in the incubator and the whole house smelled horrible until I aired it out a bit. I hope I never have one to blow up on me, but I guess it could happen. Thanks for the warning.