See also #3258 and #2385

Definitely not my area of expertise and I haven't followed the discussion about saving / autosave / revisions so I'm probably missing something. However, seems to me this is an issue of fundamental importance, as the amount of revisions that get saved is insanely big.

I've just created a new post, nothing special: just a title, couple paragraphs, a list, and an image. Then pressed "Publish" once. And I've got 9 revisions:

The amount of saved revisions can be way bigger with more complex post content and workflows. Even applying some basic formatting, for example making a word bold, puts Gutenberg in a "save draft" state, and then when the autosave triggers, a new revision gets created. This happens with any edit, also when changing a block position, or alignment, etc. Creating a post with some more blocks and formatting can easily generate dozens of revisions.

Seems to me every time Gutenberg auto-saves the post content, it creates a new revision. This can be easily observed also in the Gutenberg sidebar: while adding and editing content, the number of revisions increases. I'm not sure this is ideal, and seems to me it's a big change in how revisions and autosaves are handled in WordPress.

Creating a similar post in the Classic Editor typically saves just the post, one revision (which isn't even shown in the UI) and sometimes (depending on the workflow) the special "autosave" revision.