Looking at the Overstreet PG this year, I was reading Doug Sulipa's year end review about the Marvel Whitman. He actually says they aren't Whitman, but direct editions. I don't know if that is true, though he does state these came in Whitman bags, but the comic is not labeled Whitman, so he does have a point. Were these comics ever offered to comic shops on a direct, non-returnable basis? If you look at what he writes, the early 1977 issues he commands about 50% over guide, while the 1978-1979 issues are 25% over. He also makes a point that certain issues do not see the light of day with Ebay and states that if some of these see an auction, he wouldn't be surprised at a $50-100 sale price for mid-grade. So my conclusion is that most likely my list will probably be missing a few issues due to scarcity....
I will probably repeat some things I've said before, but I can't think of any other way to answer your questions, so here we go.
Marvel's decision to make direct-sales comics distinguishable from newsstand comics is pretty easy to date. I posted here
an item establishing the beginning as March 1979 (real time; cover dates would have been a few months later). So, according to contemporaneous reporting, comics that went on sale before March 1979 with non-newsstand markings wouldn't have been direct-sales comics. This is corroborated by my memories of buying comics at the time (and particularly by my memory of my reaction to the first visibly different direct-sales Marvels I ever saw). I never saw Whitman (or other) multi-packs for sale as brand new merchandise in comic shops of that time. I never saw new comics with multi-pack–style markings for sale in a comic shop until after March 1979 (actually, it was summer 1979, just because I didn't have access to a comic shop in March). Some loose comics with multi-pack–style markings were probably seen in comic shops then, but only as back issues, and were generally scorned as "reprints."
Just before I found a comic shop (briefly) in 1977, and again in 1979, my sources for comics shopping had been grocery stores, convenience stores, drugstores, and the occasional bookstore. Comics at each of these locations were identical, what we now call newsstand editions (for all I know, in more heavily populated areas, comics may have been sold at actual side-of-the-road newsstands; I never saw one, though). Multi-pack comics were sold in five-and-dime stores, a retail category since eliminated by the growth of Walmart. Though my shopping options in the early 1970s were limited, and perhaps not representative of nationwide trends, I seem to recall seeing single comics for sale in five-and-dimes ca. 1971–72. By 1977, though, all I remember seeing in such stores were multi-packs. Multi-packs are the source for "Whitman" Marvels. Multi-packs were sold in five-and-dimes and NOT, to my memory, in comic shops. For Doug Sulipa to conflate "Whitman" Marvels prior to 1979 with direct-sales comics is, IMO, just simply mistaken.
However, as I have alluded to earlier, that seems to have changed during 1979. See this thread
for photographs of two Whitman bags from 1979, AFTER Marvel began making direct-sales comics visibly different from newsstand comics, with the comics in the bags visibly identical to comics then sold in comic shops (and my thanks again to freakdylan for posting the photos). Clearly, during 1979, Marvel was continuing its Whitman multi-pack program, but was apparently packaging direct-sales copies in the multi-packs. So Doug Sulipa may have a point, but ONLY for Marvels published during or after 1979.