IMO- there's too much "science" and we've forgotten how to look at the results and fine tune accordingly.
I don't know about 30°, since I've never bothered measuring the angle. I use the very old method of using the "straight leg with the heel on the pedal" method as my basic starting place. Then I observe. My goal is to find the highest saddle position that's low enough that the hips don't rock.
Another consideration is having some room to push back on the saddle, which effectively is the same as raising the seat a bit. I prefer to use this when pushing up steep short climbs and it seems to create some added leverage and power (even if that's an illusion).
In any case, no method will be better than a starting place, because the length of the foot, cleat position, and bend at the ankle all play into things, and are harder to predict.
So IMO- everything is about finding a starting place, then fine tuning based on the rider's perceptions. Any rider with a decent level of experience will get on a bike and after riding for 5 minutes feel that the seat is either too high, too low, or in the right ballpark.
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