Websites consist of code to be interpreted by browsers as they see fit, for the benefit of their users. Those users do not necessarily want exactly the experience the site authors want them to have.
So, along the same lines, it may make sense to improve the UI for autocompleting users, or for hinting about the use of the field, to make it easier for sysadmins. But that shouldn't break the more common case of handling sites that just think they're Too Special or Too Important to allow saving login information.
And I would actually argue that blocking before closing the tab should be a decision up to the developer, not the browser.
The shop controls the server the user rightly controls the experience on their machine. The browser vendor provides an application that runs on the users machine. If the shop doesn't like it they can pound sand or suggest the user would be better off with a different browser.
They can perhaps rightly say that the deviation from standard is unfriendly or sub optimal but one would hope they wouldn't appeal to imaginary authority derived from a bad analogy.
A raven isn't like a writing desk and a client server interaction isn't like a user visiting a physical store.
Analogies can serve to communicate but when you use them to prove a point the only thing you prove is your lack of understanding of the matter.
I didn't realize until now that it doing the right thing from my (the user's) perspective was because it was breaking a web standard, but damn if I don't find it useful.
Then chrome Devs say to use autocomplete=something-stupid to get the specification behaviour of 'off' WTF is that?!
Donate to Firefox.
Chrome is the new IE