There's no difference from what OP is saying because you're not being paid based on how much Bitcoin you receive, but rather on its value. It’s more like you’re getting paid in USD, then buying Bitcoin every week which is still DCA. Maybe for signature campaigns that don’t base payments on USD value, like if you’re receiving 0.001 BTC per week, that could fall under BCA .
My point is there is no need of too strictly classify DCA or BCA. Companies run their signature campaigns with clear idea on how much their payment rates are for campaign participants.
Fiat, stable coin or Bitcoin, is only a payment method, but signature campaigns and companies always know that how much money they want to pay campaign participants.
$100 can be paid in fiat currency, stable coin, Bitcoin or altcoin, but the pay rate is the same.