1.2 percent is a pretty significant chunk and crypto has the potential to take all of that away, since it doesn't look like they have any resources to spare for its monitoring and regulation.
I doubt bitcoin remittances represent a significant portion of that 1.2%. Plus, those are remittances received. Remittances received in any fashion are a boost for their economy. Burundi commits barely any spending towards AML regimes as it is, so I don't think that's their primary concern.
I think the government just received lots of complaints from scammed investors and they figured this was the cheapest, fastest way to address it.