Yes, this information appeared due to the fact that Tesla is a public organization and submitted its reports to the SEC. I recently read information that in fact Elon Musk owns a much larger amount of bitcoins, namely, about five billion dollars. A significant part of them is on the balance sheet of SpaceX, but this company is not public and does not submit its reports to the SEC. Elon Musk also has bitcoins in private ownership. So the information about Tesla's purchase of bitcoins in the amount of one and a half billion dollars can be trusted.
These are just wild rumors. In case SpaceX want to purchase Bitcoins worth $5 billion, then they should have cash reserves worth at least that much. And as far as I know, the Space X reserves are around 1/10th of that amount. And even if they have that sort of cash reserves, I don't think that they will take the risk of investing all of that in a highly volatile asset such as Bitcoin. For comparison, Tesla invested less than 10% of its reserves in BTC.