In a way you are right but at the same time the whole purpose of advertising is to try to convince people to buy your products, outside of this market I doubt too much attention is given to this news, so we need to wonder are there a lot of people buying a Tesla with their bitcoin or dogecoin as a result of this marketing strategy? Because I doubt it, Musk missed his chance for his Tesla cars to become a staple of this market when at first he began accepting bitcoin as a payment option only to take it away a few days later on completely ridiculous grounds.
But there is the strategy. They don't need people to buy with BTC or another currency, what they wanted is for the newspapers to talk about Tesla, because along with the news they will give other information about the company that is already of general interest.
Besides, they're talking about Tesla. And people keep the name/company alive in their minds. And this can help in future decision making when buying an electric car.
I'll give you an example of a new supermarket company in Portugal. Use a similar style:
They only have stores open in one region of the country, but every time they open a new store, the news of this opening is broadcast in the country's main media outlets nationwide. Along with this news, there is always an interview given by someone from the company, who says that the company has the objective of opening stores across the country.
What do you think will happen, when a store is announced, in a new part of the country? People have already heard so much about that supermarket that they will want to know about it.