The Wiki page on the book backs you up on this - and if I remember correctly, writing the book form in 1985 allowed Card to add in the whole videogame angle. And then he updated it again in 1991, to reflect political facts (according to the Wiki - I'm willing to guess he wanted to erase references to the Soviet Union).
"Ender's Game" isn't the only Sci-Fi novel that grew out of the magazine space Off the top of my head, "A Canticle for Liebowitz" also did that.
I skipped over the parts about the brother and sister influencing world evvents by blogging, or whatever it was. I can see the earlier version being better.
Plenty of classic SF did
The sequels to Dune - Children of Dune was serialized on Analog too IIRC.
Also Haldemans “Forever War” was a long story in Analog.