Gallia having so many different (and new) commodities is a legacy of the house's introduction to the mod. Due to its initial (and current?) isolation, Xoria designed it such that the house's internal economy was essentially independent of the other houses, with exceptions for some inter-house trade runs. Therefore, it was no doubt easier for him to build on that foundation, despite the house being slightly more accessible; since many of the new commodities were metals, that's why they ended up in Gallia.
