Repo: first off, WY and WL are selling their vials and smack packs of yeast as "pitchable" when, in reality, there are only enough viable cells in those packages to "properly" ferment a 1.040 ale acording to industry standards - and only then when it is extremely fresh. If you need some documentation to back that up here's a great article: http://www.byo.com/component/resource/article/1749-yeast-pitching-rates-advance-homebrewing
Now, obviously WL and WY are very knowledgeable about their product, and one of the reasons they give the recommended temps is because the amount of yeast they sell in their vials/smack packs are so small. They are assuming you are not going to make a starter or pitch multiple vials, so warmer temps will work better in those cases. So I don't think those Phd's are wasted, they are just trying to cover their bases (and sell a product).
Here's an example of what I am saying: WL and WY both say that one vial of lager yeast is enough to ferment a 5 gallon batch. But they have you pitch it at 65-70 degrees and then start fermentation and lower the temp down slowly over a number of days. Anyone who knows anything about traditional lager brewing practices knows this is not a recommended practice. That is so far below the industry standard cell count as to be laughable - but it allows WY and WL to sell a lager yeast to homebrewers who may not have the equipment to chill down to 44 degrees and grow up a large enough pitch of yeast.
In other words, if someone is looking at homebrewing as a novelty, sure! The temps that WL and WY suggest, along with their pitching rates, are going to work best since you most likely won't be controlling fermentation temps and won't be pitching an "appropriate" amount of yeast. If you want to make the best beer possible you must manage fermentation and this includes pitching rates and temp control.
Regarding fusels, my understanding is they are generated at every fermentation and increase due to different factors, warmer fermenation being one of them. In that case, you should have more fusels at 75 than 65. Wether or not you can discern them via flavor threshold may be a different story but I get better head retention from cooler fermentations (head retention being directly affected by fusels) and ester profiles are certainly cleaner under 70-72.
Also, you may note that WY and WL do not follow the same pitching rates for commercial brewers as they do homebrewers. Commercial brewer's pitches are closer to the cell counts shown here: http://www.mrmalty.com/calc/calc.html
(though a bit smaller because the sterols in the cell walls are fortified where as after a fermentation those sterols are mostly depleted) and they overnight your yeast pitch in insulated boxes with ice packs and assume you will be using it with the next day or two (or week at the most). They do ship the vials/smack packs intended for homebrewers in insulated, ice pack cooled boxes but the expiration date is months as opposed to days and most likely if that vial or smack pack is over a week or two old it is in need of a starter even for a 1.040 beer. So you could see why they would recommend warmer fermentation temps.
Wow. that was a long post.