One of my supplier only wants me to do FBA and not FBM

Is it suppliers choice if I want to ship the supplier products using FBA or FBM? Isn’t that the sellers choice? We did I not signed any agreement (if there is one) but the supplier only wants the seller to utilize FBA model for most of the items that they have. Maybe supplier doesn’t trust the seller or will FBM will make the BSR lower if I choose FBM route? Maybe the supplier doesn’t trust the seller if I will ship the items on time? Supplier only have two sellers, me and one more seller. Items are not selling hot either, just want to see if it’s worth doing FBM instead of FBA.