Isn’t it the exact opposite? If it just says zone 6, it’s the old system because no a or b suffix. If the number space got doubled zone 6 would still exist but

Isn’t it the exact opposite? If it just says zone 6, it’s the old system because no a or b suffix. If the number space got doubled zone 6 would still exist but mean something completely different now. You can’t tell if it’s the old or new system at all because the first numbers all got re-used but with different meaning.