And to add to Fenella's post, I have to say a very unkind thing but...here goes:
Harry is thick not the sharpest knife in the box, bless him. He struggled at Eton - it wasn't the right school for him, I think Diana and Charles sort of knew that (and the school knew that he didn't meet their normal admission standards) but they sent him their because it was felt more important that he should be a) with his brother and b) just across the river from Windsor Castle.
The history master who taught him was shocked at his lack of interest in history and specifically his family's history. It wouldn't surprise me if I could beat him on Mastermind with the special subject of 'The Royal Family since 1900', or similar.
He wouldn't have clocked about the Letters Patent, or anything like that. And not only did he not understand these things himself, he was so stupid and unimaginative as to fail to tell Meghan, or at least to put her right, when she jumped to the conclusion that the RF were being racist.
I felt so sorry for Prince William having to do that engagement the day after the OW farce and being asked if the RF were a racist family. He answered very well and kept his composure.
I've only ever seen excerpts of the Netflix documentary (couldn't stomach the whole thing) but it's telling that Meghan's mum says something like 'I warned you - it's racism coming down the line!' at one point. Clearly she and Meghan were very ready to look for and find all kinds of micro-aggressions in her dealing with the royals.