Sorry. You missed my point.
The Amazing Spider-Man#252 (May 1, 1984)
Marvel Super Heroes Secret Wars#8 (December 1, 1984)
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7 month gap between them = No confusion which came first
The Incredible Hulk#181 (November 1974)
Wolverine #10 (August 1989)
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15 years, 3 month gap between them = No confusion which came first
X-Men Annual#14 (August 1, 1990)
The Uncanny X-Men#266 (August 1, 1990)
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0 month gap between them = Potential for confusion
So comparing the other books to the X-Men Ann #14/UXM #266 situation is not the same. They were published in the same month. That is why it is easily assumed Marvel messed up the release of this book because (1) who cared about Gambit anyway, and (2) Marvel just wanted to crank books out without a care of which order the books had to be released.
You're glossing over the gap there, there was three weeks between them, pretty damn close to a month.