Perhaps I'm asking a question?

I've just finished reading a book called 'Statistics without tears' by Derek Rowntree. It's a basic tutorial on statistical concepts focussing on the ideas and principles, rather than walking through actual calculations in any detail. I found it useful and would recommend. But I'm here to talk about language, not statistics! 

The book is written in what I would describe as a very 'careful' style. You know it - the way older academic writers tend to, with quite precise attention to punctuation. Even though the tone of this book was very informal, friendly and not at all stuffy, I felt that every colon and dash was considered. 

So it was interesting to me that both times Rowntree used a sentence in the form Perhaps you recall..., he ended it with a question mark: Perhaps you recall the idea of a confidence interval? (p.183). I've had a quick look around the internet and can't find much on this topic other than a few sites peeving about the use of a question mark with perhaps, saying that it is not necessary and therefore wrong. There are people asking about it in English forums, indicating that it's something that might feel natural. 

It seems likely, then, that it's a 'declarative question' - the same as if he'd written You recall the idea of a confidence interval?. These are common enough, though definitely I would say a feature of less formal writing, just as contractions like I'll or don't are, which Rowntree also uses throughout. But it is interesting that he doesn't use this form - he uses perhaps. The question mark itself is enough to allow the reader to see that it's a question, and to therefore know that they are not being told that they do recall the idea, but rather prompted to agree that yes, they do recall that idea. So perhaps adds a bit more prompting, a bit more questioning, a bit more possibility of you not in fact recalling the idea of a confidence interval but that's absolutely fine because it was a few chapters ago and it's complicated stuff so don't worry.