Did you actually read the thread you posted? Where they state tuning down half a step gives you A=415.3?
I guess not.
"This adjusts where the note "A" is exactly. 99% of the time it's at A 440, but in some rare instances, other standards are used. For example, in many orchestras, it's not uncommon to tune to A 442 or A443. For half step down tuning, A 430 (which is usually a low as tuners adjust) is nowhere near enough to reach the next half step. What you'll want to do instead is
just tune to the next note down, which would be Ab/G# (which happens to be 415.30 Hz). Or if your tuner has the option for low-tuning guitars (usually the flat symbol: "b"), then use that. The Hz adjustment on the tuner is for shifting the entire tuning system by minute amounts."
Thanks for posting information that proves my point..