I have that language for that task as well and I interpret that to mean that the charge date on the credit card has to be within the promo period. So there would perhaps only be issues for pre-paid stays if a property actually does charge in advance.
Worse is that on ONE (but only one) of my stay related tasks (the Weekend stay one), it seems to indicate that the booking has to take place during the promo period:
"Number of bonus points listed above will be awarded after member books and consumes required number of Qualifying Stays, including a Saturday Stay and for a minimum of 2 nights, between 1 January 2018 and 30 April 2018 (both dates inclusive)"
Compare that to the language on all my other stay related tasks, such as:
"Number of bonus points listed above will be awarded after the required number of qualifying room nights have been consumed by the member at any IHG brand hotels between 1 January 2018 and 30 April 2018 (both dates inclusive)"
The language of 'booked and consumed' has been in a few offers in the last few rounds of Accelerate. In my experience, it does indeed mean you have to book in the specified period.