The film of this whole encounter is available on twitter, should you care to look at it (fairly sure you won’t, since it shows your post is completely inaccurate).
From that you would learn firstly that William congratulates Mia McKenna-Bruce on winning the Rising Star award, and immediately says “I’m sorry I haven’t watched your film yet, but I’m sure you had a good time making it”. To which Mia immediately replies, warmly and smiling broadly “We did, we had a really, really, really good time!”.
So the actress was not remotely upset by the question, nor did she seem to find her recollection of working on the film traumatic. Nor was anyone else there concerned by the exchange - they were all also smiling broadly at Mia while she answered William. He then immediately again apologised for bring behind in his film watching.
Secondly, this harked back to a conversation he had, also on camera, when arriving at the event, and speaking with Elaine Bedell, chief executive of the Southbank Centre. William apologized for his wife's absence at this year's awards. "I'm sorry Catherine's not here. She does love the BAFTAs," he said.
"I remember last year about the films that you'd watched," Bedell replied.
"All the ones I watch, she watches with me. So we go through it carefully," William shared. He then mentioned that he’s unfortunately not had the opportunity to watch many films this year.
Manufactured outrage, in any event.