The bike builder's lead guy has said he'll look at upgrading the alloy across his range for this frame design. Again, it isn't a custom build. If he's willing, I'm down. If not, I go elsewhere as you say.
Regarding the tubing maker, the frames are to be built in small batches in Asia. The builder (really the bike builder) doesn't disclose all his supply chain details, for better or worse, and it may be that his frame supplier keeps his cards close to his belt as well. There isn't the openness you expect from a bespoke builder, and there won't be.