This is not alternative. This is one of "fake" MBO.
Do you see, they don't even call it as Mbo. And that's correct.
They just use L2 data changes to simulate Limit orders Adding and Removing.
But this method is complete nonsense.
Using L2 data you do not know which specific order is removed from the queue or which of them is modified.
At the same time, Bestorderflow uses real L3 data, also known as MBO, to reconstruct the real queue of limit orders.