The GN is certainly a foob, as they (apparently) never had a hopper with a peaked end, and all of their three bay hoppers had more ribs than that. The lettering seems to have been based on the ballast hoppers, so is a legitimate scheme, although it doesn't seem to have been used on ribbed side cars. The GN might have used it on these, though, if they had bought some.
They did buy/lease used three bay hoppers, so the IDEA of them having these isn't implausible. I won't buy them, but if BLI wants to sell them, more power to them. I have Bluford's cars, and have the new Atlas cars on order, so should have enough hoppers.