No it's not, as far as a I know. There is a somewhat utility-free provision to get space on flights which are full but you certainly have to pay significantly for that, in the unlikely event you can get it to work.

Same Day Change applies to many shorthaul flights, not a Gold benefit.

Avios bookings are changeable up to 24 hours before original departure (fees apply).

Some Avios extra availability shows up for Golds, but typically over the middle distance and in WT/ET only, and on BA metal only.

Avios redemptions do often show up on the day of departure, but if you have a booking already and you're within 24 hours this rarely helps.