If there was ever any thought that Harry (and Meghan) would not be fulltime working royals—the Queen would not have given them the Commonwealth roles she did. Nor would some of the patronages been passed to them.
IMO, This is a story dreamed up by Sussex fans to present their heroes in a more positive light.
Not sure it is a dreamed up anything. People are just going by what it being presented. That is the new version of events. I actually agree that I don't think talks of a slimmed down monarchy was the sole reason but I do think Harry knew it was going to eventually happen. So it played a role. Not a major one but I would be surprised if at one point he didn't mention it.
As for that statement itself, Valentin Low from The Times has posted an interesting article on what he seems to have learned about what took place in the days leading up to it.
https://www.thetimes.co.uk/article/harry-and-meghan-ignored-aides-advice-about-quitting-j7ggx9bnm
The whole thing just sounds unfortunate and a mess. I really don't think anyone is particularly happy right now and they need to find out who this leak is. People claimed it was a Sussexes to sped up the process but Dan Wootton went on record saying that he was working on this story for 2 weeks and that their people tried to stop him and Low's article seems to confirm it. His source is within BP.