I am reading the Harry Potter series recently and I have difficulty in understanding the following 3 examples:
1) What could he have been thinking of？It must have been a trick of the light.
2)But then it struck Mr.Dursley that this was probably some silly stunt--these people were obviously collecting for something...yes,that would be it.
3)He'd never even seen the boy.It might have been Harvey. Or Harold.
I think these three examples are all expressing Mr.Dursley's mental world by the author's speech, and that's why there's a 'have' after 'must' and 'might' in the first and third example. Likewise, the last sentence in the second should be 'that would have been it.' in my opinion.
Help me out with this. Thank you all.