An article in The Telegraph said:

However, the Duke is understood to have taken particular issue with the notion that the couple were to be treated as private citizens. If that were the case, it was claimed, such formal guidance would not be required.

The Sussexes prefer the term “public figures”, and would have liked an acknowledgement that, on a personal level, they remained members of the Royal family, despite no longer receiving public funding.

The article was quoted in the St Meghan Markle reddit.