Page 554 of Collins English Usage reads
You cannot use a pronoun and 'be' after an adjunct:
✳At the top of the steps it was.
You say it was at the top.
Why is it so?
Does this apply to other copulative/linking verbs too?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
It's not always true, especially in spoken English.
English, as well as many other languages, is built around constructions that go subject-verb-object. Of course, there are complete sentences where no object is required (eg 'The dog barked'), but in complex sentences, it is unusual for a verb to appear at the end of the construction. When it does, there is an explanation for it, but you are asking for an explanation for the norm, which is a backwards way of looking at it.
While written English is more likely to observe rules, spoken English doesn't. These might be heard in spoken British English, particularly in some regional dialects:
As a general rule, your quotation is correct, but there are plenty of exceptions.