Fair enough on all accounts. When I prepare the soil for planing, I make sure I mix it throughout the growing area, you're right about the bathtub effect. Amending only in the immediate area you're planting inhibits growth in the long term, and possibly worsens conditions in the short term (in a raised bed setting, it's a good idea to loosen the soil where the raised bed is going, if applicable, for the same reasons).
When I say a healthy amount of bone meal, I mean a light dusting in the bottom of the planting hole (usually less than a tablespoon), which is then mixed in the surrounding soil before adding another light layer of dirt and finally the plant itself. And this is usually only when I prepare a bed for the first time- in subsequent years the soil doesn't need as much amendment for the most part. I just loosen it a bit and plant as usual.
Tilling your bed year after year and adding more fertilizer just causes organic material to be broken down faster. You will need to add new organic material occasionally, but the rate of application is exacerbated by over-fertilizing. Many of the nutrients should already be bioavailable to plants, possibly with some light additional ferts when the plants need them.
