For example I can post and get my bitcoin through signature campaign and payment in Bitcoin forum. If I am considering it as my Bitcoin Cost Averaging, it's nothing incorrect or unacceptable.
Is it wrong if I say I am doing Bitcoin Cost Averaging with $40 weekly from a signature campaign?
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 .