according to the BA website exit row restrictions apply until 24 hours before departure for :

long haul for silver

long and short hall for bronze

https://www.britishairways.com/en-gb...ving-your-seat

Silver/oneworld Sapphire Free seat selection (excluding exit row seats on long haul flights) from the time of booking
for everyone in your booking. Exit row seats on long haul flights can be selected for free from 24 hours before departure*.

Bronze/oneworld Ruby Free seat selection (excluding exit row seats) from seven days before departure
for everyone in your booking. Exit row seats can be selected for free from 24 hours before departure*.


Flex Plus would however allow seat selection, it could be for this weeks flights the op has a flex plus ticket (the op has said this trip is not hbo)

Tickets with increased flexibility allow you to make certain changes to the date and time of your flight. They also include free seat selection:

• Flexible fares (Plus Flex) allow you to reserve seats for free from the time of booking.
• Semi-flexible fares (Plus) allow you to reserve seats for free from 48 hours before departure.

or it may be these flight an with an agency that allows seat selection
or it may be am it glitch

at first glance it would appear what BA currently says is different from what the sticky says