It's a very strange story because no one seems to benefit. But Victoria Ward seems quite balanced normally, at least in comparison to Camilla Tominey, so she must have had a source. Perhaps its someone from the sidelines/ a RF courtier or Sussex staffmember acting independently.
It makes no sense for Meghan to stay away due to these letters. But the article also mentions H&M gripes about Archie and Lillibet not being included in the coronation plans. Harry said ages ago that they'd come to the coronation if some problems were ironed out, the ball's in the RF court etc. etc.
I'd say it's pretty obvious those conversations weren't productive from the Sussexes point of view which is the real reason why Harry is coming alone.
This is what the Telegraph article said about that:
The Palace is also aware of the Sussexes’ frustration that initial email correspondence about the Coronation made no reference to their children and their potential involvement. The omission only fuelled their feeling that their family plays second fiddle to the Waleses.
Following the late Queen’s death, the Duke and Duchess confirmed that they would like their children, Archie, three, and Lilibet, one, to use the Prince and Princess titles they had automatically inherited.
But the Palace’s delay in recognising the children’s elevated status caused frustration, not least as the Prince and Princess of Wales’s titles, and those of their children, were swiftly changed upon the late Queen’s death.
The Duke of Sussex made clear in television interviews in January that he was holding out for an apology from his family, when he insisted he wanted to reconcile with the King and the Prince of Wales.