No, I don't see anywhere where it says the stay has to booked during the promotion period to earn the 1000 bonus points.
The T&Cs:
say:
Members residing in a participating country, territory, or region who (a) register for the Promotion (either on bestwestern.com/summer or as otherwise permitted (e.g., at the front desk of any Best Western branded hotel in the United States, Canada, or the Caribbean Islands)); (b) on beswestern.com, the Best Western To GoŽ mobile app, or the Best Western mobile site, book an eligible stay to occur during the Promotion Period at any Best Western branded hotel worldwide; and (c) complete said eligible stay during the Promotion Period, will earn 1,000 Best Western Rewards bonus points
My highlighting shows that it says the stay has to occur during the promotion period, not the booking. "Book" is a verb here, but the phrase "to occur during" would modify a noun, and the only noun that precedes it is "stay". So it's the stay, not the booking, that has to occur during the promotion period.
On top of that, I can't recall any
previous Best Western promotion where the stay had to be booked during the promotion period either.
However: What it does
seem to be saying is that it may not work if you take a reservation that was originally booked for a stay outside the promo period, and you change that reservation to a date that is inside the promo period. It
might require a fresh booking in that case. (That's how I read the separate clauses that first you have to book a stay which is scheduled to be inside the promo period, and then you have to actually stay inside the promo period. Just doing one but not the other, because you changed the reservation dates, may not count.)