I don't believe it's a blanket requirement, it's rather that if you want to market your product as being Halal then you have to get certification. Perhaps have a look at lemparin2020's comment https://news.ycombinator.com/item?id=24518270 who appears to be an actual Indonesian who is more familiar with the article's subject matter. lemaprin2020 says:

>>Well obviously. If you want to build a halal certified banking product it has to be implement syariah principles, thats the point.