So your explanation for an old url being rewritten, losing rank and then changes being made and fetch used a second time to enact instant change as G promised on penalised urls at a time when huge core algo changes are being undertaken, is? Coincidence? The URL was rewritten at a time of heightened algo activity. Not merely a drop in rank due to a better match.
Perhaps Panda was tweaked and to help webmasters see an ongoing penalty url rewrites occur and or Panda was tweaked as part of the core algo and this change occurred anyway and or Penguin is running as the core algo now and they're going to inform us some time after. "G has said it's not Penguin" Like they haven't understand previously. Perhaps they're slowly releasing the new Penguin attributes as would be expected for an individual algo being merged into a core which WILL happen this year. "Last July, Panda 4.2 was slowly rolled out... It was so slow people didn't believe it."
I think just maybe, if a website is currently suffering a current animal penalty which I believe this one is, that at the very least, this ongoing core update might have affected that slightly and seen these changes on that URL made. I actually don't know why it picked out that URL exactly but I've made similar edits to a dozen other pages - not that any of those urls got auto changed so I'm not expecting similar behaviour.
I wrote the following last night. With regards to the importance of title. Having just uploaded one article and searched on the target phrase which is along the lines of;
Brand Widget Field
Out of the top twenty results, I went in fifth (this morning, 2nd). 1 to 4 and 6 to 12 and 14 to 18, 20 have no mention of the brand in title, no mention of brand in url and only brand mention in displayed description. There are other relevant pages with keywords in title / url / on page.
A widget synonym is present in all the titles as is the field. Half have synonym of widget in url. The next similar page to mine is in 13th with brand mention in title and url, the next is 19th. I dare say they lack the content I have written.
The stand out aspect is that on two pages, only three are what I'd term are usual G historic results, with adwords correctly targeted titles being the obvious places to click. I wouldn't click on any of the other nine results on the first page if considering just the bold title.
I'd click on mine (or adwords) ha but that's partly good news I suppose. So based on these results, yes title not crucial to Google but crucial for webmasters. I'm not going to stop including detailed titles as evidently they will aid in CTR but I will reduce synonym use and again shorten urls more in line with the October mobile update. (You see I don't always react on the cusp)
Obviously, scientifically, unless run same manual reaction on more urls that were changed and knowing why those urls were auto changed, it could be a variety of reasons. At least two other users on here have experienced what I have, I may re-read posts and find out who they are and ask if they can try what I did.
I'm not an expert at this, I believe the site in question is suffering a current penalty. I just notice things occasionally. I knew something for a year and one in business SEO'r said to me, "you know I thought you was insane, turns out what you're doing is being recommended by another also..."
I'm not saying I'm right, I just notice things sometimes and that's what the forum is for. If it was based on substantial fact only, we wouldn't be able to reply to the January 2016 SERPS thread until at least July 2017 and with properly worked out case studies, tests, examples and comparisons gathered, but by then, it wouldn't matter. I'm going to be wrong more times than not. I just reported an automatic change and how I reversed it. Someone else experiencing the same might thank me, many others who think I'm cuckoo won't care either way, some might even berate me.