When I said that I agreed with Mr. Frankel, I added the phrase "for the most part" to indicate that I, too, acknowledge that the ad-libbing and unscripted humor is what we all tend to remember most about I Spy. At the same time, as a freelance writer myself (okay, I write about sports, but still), I can sympathize with the plight of writers who have their words changed after working so very hard to craft them properly. In my case, it is an editor who takes great liberties with my articles despite my pleading with him not to do so. He seems to feel the need to insert a bunch of extranneous words to "explain" things to the readers - things which I believe the readers are intelligent enough to figure out for themselves. I don't like to spoon-feed my readers and I don't like to insult their intelligence, which is what his "enhancements" do.
I have been fortunate to correspond with a famous writer of another very successful TV show, and when asked whether there was any adlibbing done in his show, he always says, "If it isn't on the page, it isn't on the stage." This seems to be something of a credo among writers as concerns actors, so it's not surprising that Mr. Frankel and the other I Spy writers would have their feathers ruffled by all the improvisation that took place.
Overall I suspect that, as in most situations where there is a conflict with strongly divergent opinions and recollections, the truth lies somewhere in the middle. No doubt the adlibbing and humor of Mr. Culp and Mr. Cosby was critical to I Spy's success, but perhaps there were occasions when they took it a bit too far or interjected it at an inopportune moment.