The gacha formats are very specific (e.g: how the probabilities are distributed).

In many countries it is required by law to specify to the user what is being purchased. Because of this, it is very easy to track / verify that one system is equivalent to a specific form of gacha.

Then, it is widely accepted that loot boxes are based on gacha. The Wikipedia article for loot box has more context in this regard.

https://en.wikipedia.org/wiki/Loot_box#History