I’m sorry but that can’t possibly happen. An editor can’t even change a single comma without the express consent of the author.
You haven't dealt with many editors. Unfortunately, editors can and do change all sorts of things without the writer's permission. There are some true horror stories out there, including having an editor go through and remove every last contraction in an entire novel, and doing so just before galley proofs were sent back to the writer.
In this case, the writer had no time at all to go through and correct the idiotic editing.
Not all editors are good at the job, and not all editors think they need permission to not only edit, but to essentially rewrite the entire blasted book.
A good editor tightens, suggests cuts, a good editor and looks for things such as plot changes that he thinks can make a book better. But a good editor should not ever change the writing, othe rthan correcting minor grammar mistakes and the like.
There are many great editors out there, but there are also a lot of editors who think they're the writers, and they can and do make all sorts of changes in the writing itself during the editing stage. With luck, the writer has enough power to say, "STET the whole damned thing", but many writers don't have this power, and many others are afraid to use the power, even if they do have it.
Editors can be just as wrong, every bit as pigheaded, and just as arrogant, as any writer out there.
I've had proofreaders, for God's sake, who are not supposed to change content at all, remove everything from single sentences to entire scenes that the editor loved, that I loved, and that we both thought added to the book. If I weren't a very careful and meticulous galley reader, I would have missed several of the cuts. As it was, with less than a week to get everything back to the publisher, I had to work like a slave to get everything back the way it belonged on time.
A godo editor is a wonder to behold, but there are many bad ones, and they can screw up anything.