I think before the wedding she was carried away with all the positive publicity and the novelty of being married to a Prince and the cachet it was giving her. Also I'm fairly sure Harry exaggerated what would happen after the marriage - or perhaps he didn't remember / fully understand the situation himself.
He probably vaguely remembered Kate and William living in Nott Cottage and then getting Anmer and the big KP apartment after they were married. It probably didn't sink in that they did three years including a period after George was born between Nott Cottage and the Welsh farm house they were renting.
They were given Anmer Hall as a wedding gift but it took a while for them to renovate and move there during William's Air Ambulance stint.
If Harry and Meghan had stayed and followed the same timeline they would have lived in Nott Cottage from 2018 until 2020. Taken a country residence as a wedding gift from the Queen, and then after three years upgraded their London residence or commuting distance residence.
So all that moaning in Space about how shocked Harry was seeing William's big KP apartment and comparing it to Nott Cott rang very false because
- The first time he noticed the difference between the size of Nott Cott and William's apartment was the day he visited with Meghan. They moved into the apartment in 2013. Harry was photographed inside it when the Obamas visited in 2016.
- He should have known that Kate and William managed in Nott Cott for three years and that he was going to move on eventually to something better too.
That scene describing how it felt to look around at W&K's apartment furnished with antiques etc sounds like it came straight from Meghan - she might have been shocked at the difference in William and Harry's homes but Harry can't have been he's been in and out of residences like that his whole life.