I've read speculation that the inclusion of Finding Freedom would have probably allowed a delay to allow her team to prepare. So that moves the date back to around April (just a guess). The English courts are closed in August and September, re-opening 1 October (think that is right). So her team could have presented a reason why April, May, June & July weren't possible. Then the trial calendar automatically jumps to October.
It feels like a medical reason of some sort, most likely, and her team actively wants the pregnancy speculation out there, but long term treatment for 'something' could also fit and without wishing any ill on the child called Archie, some sort of treatment for him might also be a reason.
I did think she wanted the trial and to have her day in court with all that media attention she craves. Now I think she's realised she's deep in the brown steaming stuff but can't afford to pull out and pay the Mail's costs. And she really, really doesn't want to hand over the text & email evidence, does she?
Mark Stephens on at 9.43 is interesting. He thinks that the delay inevitably leads to speculation about 'the pitter-patter of princely feet' but he thinks she's finally woken up to the problems of honest and full disclosure of her WhatsApp and emails.