Your narrative still does not ring true. The last thing they need is bad publicity.
This is a non-story that has been blown up tbf.
H&M are demoting themselves to minor royals just like Eugenie and Beatrice - who both have titles and one lives in Ivy Cottage in Kensington Palace. So they will be pretty much like the other cousins really. It was Anne's choice to take away the Philips titles. Don't really see H&M being too bothered about titles, since they removed them from Archie.
As for paying back Frogmore renovations. Frogmore does not belong to them. It was already earmarked for renovations, so would have had them with or without H&M. If the other grandchildren do not pay rent, then why should H&M, if they do, then so would H&M. If others have protection, so should H&M.
If they just took off, there would be outrage about them leaving their charities hanging.
To me it looks like they are tidying up to eventually move away from the firm - financially, but will probably still see everyone at a family capacity. The fact that H is born royalty, there is really nothing they can do about that or that their names.
So they will probably go on Philanthropy work for charities like the Obamas, Gates, Buffets etc. hence the need to keep their presence in North America.
You would have thought the critics would be happy with this arrangement. But damned if they do, damned if they don't .