CW, over the years I've done a lot of revision work on my stories which has mostly been a case of improved word choice and word order - you can see the differences in style by comparing Ed's New Life with my Rivers Region stories. One of the old stories I started over a decade ago and haven't finished, for various reasons, recently had a major rewrite where I cut out about a quarter of it by removing the sex scenes, and it's been improved in the process. I took out the sex scenes because they all related to sub-plot I decided to drop, thus it's a rewrite of the story not a revision. I hope to finish that story this year.
In my personal author's dictionary, removing something that doesn't work isn't rewriting the story, it's merely cutting the chaff so you make the entire story stronger. What I consider 'changing the plot, is adding entirely new plot lines, changing the ending, or modifying the characters motives or in my case, creating an entirely new cast. In my dictionary, that's not rewriting short segments at a time, that's writing an entirely new story with a few similarities to an older story, but it's still an entirely new book. In order to differentiate in readers' minds, I'd even give it an entirely new title, a new description (to capture the new theme of the book).
I've been known, in my 'revision phase, to cut out a 3-chapter subplot because it doesn't substantially move the story forwards, only shifting it sideways for no real purpose (i.e. it's an unnecessary distraction to the basic story). Granted, I don't do that very often, but I consider it a necessary surgical procedure to make the entire story healthier in the end, similar to cutting out a cancerous growth that makes someone sick and shortens their natural life.
In the end, I consider a 'rewrite' to be changing the entire thing, either each individual chapter, or rewriting the entire book from scratch (which almost guarantees it'll end up at a completely different destination.
I also did that with my original Catalyst, the one I never used. I rewrote the entire first book, taking it from New Orleans and transplanting it to Chicago, leaving the characters intact, but rewriting the entire thing but keeping the main plot points the same (same plot, different words). I abandoned the rewrite, because once I started monkeying with it, the plot began to morph into an entirely new story, and I liked my original story. Thus, to save the great stuff I'd already written, I revised the entire story, taking what I'd learned about the characters and their troubles to enrich the existing story using the existing text, but merely 'adding to' the existing story (i.e. the plot didn't change in the revision, but I added a LOT to the actual story in terms of meaning, character development and how the entire story unfolded.
I guess that's where I get my definitions from. It's not just an idealized version of what Hemingway did, it's based on my experiences in creating a 'workable' version of my failed first attempt at writing my Opus! The second version failed too, but it taught me enough about the characters, to write a successful captivating story.
Unfortunately, now, like you, my writing style has changed so much, that I no longer feel that 'revised' version is written well enough to reflect my best efforts. So I'm once more, considering a complete rewrite, but this time with the understanding that I don't mind if it goes someplace completely unexpected.