Suit has merit & "that" is a solved problem
"That anyone really believed the hype surrounding Siri, I'm even more amazed that people bought into so easily, I'm even more astounded that they think it is a reason to sue over, and I am flabbergasted a law firm has taken it on."
Apple fanbois believe anything they are told.
As for being astounded, why? False advertising is illegal, so if Apple is misrepresenting the functionality of their product in an ad, then people have a case to sue over it. Scientific and R&D advancements bring new products onto the market all the time, it's not up to the customer to know "Oh, well, language processing hasn't advanced that far yet." It's up to the advertiser to not claim the product does things it can't do. Not saying they should win, or whatever, but certainly there's cause to potentially sue.
"To be fair, natural language processing is a tough nut to crack on the best of circumstances, and asking a computer to figure out the referent to "that" in that kind of situation requires much more cognitive nimbleness than you might think. "
Infocom had that problem licked by the late 1970s for the common case. See Zork and almost every interactive fiction ever made. It's not tricky at all to look back 1 item in a conversation, to understand "Schedule foobar at 4PM..... Make that 3PM." means you want to schedule foobar at 3PM.