I talked to a Business Team contact about this and they said stores are stocking a 14" M3 Max Ultimate config with 64GB/2TB this year, but that no stores will be stocking a 16" M3 Max Ultimate config. With M1/M2 generations stores always had a 16" 64GB/4TB config, but not anymore, any 16" above 1TB needs to be a custom order. Apparently this won't be changing as more inventory becomes available. Seems like a strange policy change!
I guess I will go ahead and make my BTO later today..