@Angrycat2768 I agree I think a lot of this is down to PH rather than MM.
It is very clear he did not tell her a lot of what she needed to know e.g. curtseying, letters patent etc. I suspect he thought she would not marry him.
There were also clearly cultural differences US vs UK e.g. the “wedding” rather than a blessing. Had MM said the Archbishop conducted a private blessing 2 days before no one would have cared saying ha ha we got married 2 days before was not true. Harry could have explained that.
Harry had the opportunity to correct the OW interview either before it aired or just after, instead he left it until after Spare was published to row back slightly.
The bottom line is OS has either seen or been told about private letters between KC and MM. The question is who leaked them?