That was a disappointment, I agree.  The special was cancelled due to the DC Implosion, and the material from it was not published until a year later.  Starlin says he drew it expecting Joe Rubinstein to ink, and left his pencils rougher because he knew how Rubinstein would finish the art.  But when it came time to complete the work a year later, Rubinstein was no longer available and that's why Dave Hunt was assigned.

I don't think the editing was done to "show Starlin who was boss" but rather to make it fit into two regular issues of the comic.  The most puzzling thing to me is that they took a 48-page story and wound up only using 31 of those page, writing off the other 17.  I wonder why they did not simply extend it to a third issue, which would have enabled them to print the story more or less as originally conceived.  It's bizarre that they wrote off 17 pages of Starlin art.

So, again, I blame the LEGION editor for picking Hunt, as well as dumping Starlin's 17 pages.  (And if it sat around for a year, it's not like they were rushing to meet a deadline.)  And, actually, I asked Starlin about the issue a couple of years ago at Comic-Con and I forget exactly what his answer was, but I think that's where I got the "editor showing him" impression.