Interesting, it seems that the offer you receive will depend on your prior usage of the card. I have been using my BoA Cash Rewards card frequently on 'Online Shopping' since I opened it in Jun '19. I received the following version:
"Earn up to $150 cash back on online shopping
purchases through December 31, 2019. That’s a 6%
bonus on up to $2,500 in purchases—and it's on top of
the rewards you already earn with your credit card.
Maximize your rewards
Change your 3% category to Online Shopping for the
holiday season—or choose Gas, Dining, Travel, Drug
Stores or Home Improvement and Furnishings. You can
change your 3% category once each calendar month at
bankofamerica.com/maximizemyrewards."
Now the fact that it mentions that the bonus applies 'on top of the regular rewards' seems to indicate that the final cash back rate you will get if you set your BoA Cash Rewards category to 'Online Shopping", will be 3% (regular reward) + 6% (targeted offer bonus) = 9%.
And if you are a Platinum Honors customer, it nets to 3% x 1.75 + 6% = 11.25%.
This is just mind-blowing especially given their 'Online Shopping' definition is extremely broad (any non-store purchase, with the exception of Utilities, Home Cleaning or Insurance).