So it would seem there isn't one answer to this question. The answer appears to be determined by 3 factors: maturity of plant, indoor/outdoor and if we are counting on observable changes (pistil/bud formation) or internal hormonal changes resulting from a change in photoperiod.
12/12 from seed would give entirely different results, as would forcing flowering of an immature seedling. So this wouldn't give a general rule able to be applied to all. We should be discussing in terms of mature plant (as an immature plant will need to become mature prior to budding, immature plants don't flower).
As for outdoor/indoor, I'd suggest that flowering of outdoor plants is again based on plant maturity, with influence of photoperiod - though not dependent on exact 12/12 daylight hours. If a plant outdoors is mature, it will begin to flower irrespective of photoperiod (assuming it is provided with a short enough* photoperiod)
*this could vary greatly depending on a range of factors, including latitude, strain and aspect.
Decided on if a plant is flowering based on either physical/morphological observations vs internal hormonal changes is a subtle one. They aren't mutually exclusive, with one dependent on the other. This I guess is up to the grower - but would relate to photoperiod most of all, and again based on plant maturity.
All this arguing about which is 100% correct, when people use vastly different growing styles seems pointless. To determine the answer, it must be considered with the growers methods.