tense - Facts in reported speech – to backshift or not

Are these two sentences right ?

1. Mona told me that London was the biggest city in England.


2. He wanted to know where Manchester was.

I found these two sentences by chance in exercise book belongs to ministry of education in Egypt.

I mean that both sentences talk about a fact and it's unreasonable to change the tense in reported speech to past simple as what the sentences talk about is still true. (As my teacher and the books say.)

Or it's right when we talk about facts to change the tense or keep it both are correct?