It's the same as any asset or revenue stream. They have to report their overall GAAP bottom line only at the end of a quarter but even then don't need to legally report the specifics.

Usually it's reported for shareholder interest and to attract investors. They can also hide it among other business divisions if they want to, risking investor backlash. Like how Microsoft used to show Azure revenue.

https://arstechnica.com/information-technology/2015/12/ballm...