I remember knowing someone that felt it was best to keep the night/day temps very close and he had killer yields... I'll try 2 get ahold of him n see why he thinks this.
I think the budrot thing is that when the temp drops, if there is moisture in the air, colder temps will cause it to condense faster, course god proper ventilation could solve this unless you are like in the tropics...
Yeah ventilation is the key to avoiding bud rot but high enough humidity is part of the cause. Anything above 65% you need to be careful of or better yet avoid. That's why it's recommended not to let the humidity get much above 50-55%. Your friend's temps were good for lights on and you don't have to have that big change in temp to get resin to form, it's just believed that the temp drop at night helps it to form better. Although this isn't exactly proven but rather theory, at least when I first read about it.
I think your friend's yields was more a matter of good food and care then it was a factor of minimal temp fluctuations.