Probably some truth to the stuff...I just question the cost vrs the actual commercial need. Old timers used to apply motor oil to the underside of the deck and (so I was told) it would take several applications over the winter to "set" into the metal....and no there wasnt enough to hurt the grass. Commercially speaking...The cost just isnt worth it on a large scale. Once you learn to grow grass to the apropriate height..you stop spending money trying to figure out how to deal with all that grass....cause there just wont be enough to cause a problem.
i have "learned" to grow less grass top and more dense a the same time dude and when rain happens and you cant mow you are forced to cut tall wet grass and it clogs the decks pretty bad sometimes depending on the moisture actually on the blades like heavy dew(the worst) so you should not try to be such a smarty pants as it is not appreciated here in that fashion.
we personally do not use any deck treatment and have to scrape the decks often this time of year, multiple times per day even and there is nothing to do about it save trying fluid film or slip plate etc. i may try this for the future but right now we are so busy i dont think i could give the underdeck treatment enough time to set properly and it would not last