If it was a first run, pages would naturally have yellowed over time.
No reason whatsoever that someone would have a single copy sealed in some kind of noble gas filled storage container.
Even the finest comic specimens ALWAYS have yellow pages.
The covers may be crisp and pristine, but the inner pages?
I think this has to be a very well done fake.
As a collector of vintage paper items (including quite a number of old comics, going back to the early-1940s), there can be quite a difference in paper quality, depending on what kind of environment they were stored. I’ve seen and owned a few examples which have amazing fresh, off-white paper, with no yellowing or browning. Rare, but if some old comic was nicely tucked away in a stack of mags, in between two larger magazines (like old Saturday Evening Posts), in the attic of a dry, western or mid-western home’s attic for decades... the paper will retain a surprising whiteness and like-new flexibility. The acids within the paper haven’t had a chance to degrade it.
On the other hand, I’ve seen examples of comic books that seem outwardly untouched and otherwise in ‘new’ condition... but they were stored in attics in hot, humid locales, and the pages will be brown and brittle. Even breaking apart upon touch.