Ok wow......
Different pieces of wood can contain different levels of tannins, so many variables come into play on the level of tannins released from wood and the amount of purigen required to remove it. 1 bag isn't going to remove it for everyone. They may have a denser wood. Some hardwoods have a rich red colour to them, you can boil them for hours and still get coffee....
I think the dirt is going to give an extra kick too. Like come on, how much more natural ferts do you want to get. Put water sprite a known fast growing plant in three tanks all have the same lighting same water volume and levels of co2. Only difference is they all have different substrates with one being dirted, one sand and one gravel. Which one is going to grow the quickest???
I've never had BBA in any tanks some run co2 some don't. Nothing is high light but medium to low. I've had diatoms for a sustained period of time but that's it, it's good when it goes I remember that I have to dose ferts again. If I forget to turn my timer on before going away after fiddling with the tank with the lights not operating on the timer then I may get some BGA....
BBA doesn't grow no matter what just for people who are arrogant and stuck in their own ways of thinking they're right.
Good day