My guess would be that it's the same sort of thing as these issues:
These two comics have virtually identical interior pages (IIRC, the indicia are different in the two comics). Furthermore, there are direct-sales AND newsstand versions of at least the Doctor Strange/Ghost Rider Special.
Why would Marvel do this sort of thing?
Well, Ghost Rider,
at this time, was being distributed to newsstand outlets by Curtis, Marvel's newsstand partner of (then) some 23 years. Doctor Strange Sorcerer Supreme,
I believe, was being distributed to newsstand outlets by another distributor (identity unknown to me). So, publishing a crossover between the two titles carried the risk that, in some markets, readers of the GR
chapter (with saturation distribution) might not be able to read the DSSS
conclusion (with perhaps more spotty distribution). I believe that, to prevent reader frustration, Marvel elected to publish the DSSS
chapter as the Doctor Strange/Ghost Rider Special
one-shot, to be distributed by Curtis, thereby allowing all readers the opportunity to read both chapters of the crossover.
Of course, if direct-sales retailers found out that there was an issue distributed to newsstands that was NOT made available to direct-sales shops, they would have screamed bloody murder (never mind that they had the story in their copies of DSSS
#28). And so Marvel had to publish a direct-sales version of the DS/GR Special.
I believe similar marketing objectives can account for the two versions of the Quasar
#1 that you showed us.