I've always found the idea of tilting a bonsai pot off. The holes arent ar the edges. They would fill up to the hole before draining correct?
Or are we saying the rain will run down the slope and not get absorbed into the substrate? You'd need to tip one up quite a bit wouldn't you?
Consider the case of a pot so shallow that its depth matches the saturation depth of the substrate/medium/soil. Raise one side of the pot, some water drains out (maybe by overflowing the down edge) and the roots on the elevated side are above the saturation level.
By extension, similar things happen with a slightly deeper pot and one slightly deeper yet, even with no loss of water from the pot - roots on one side are above the saturation level and are well aerated, at the price of roots on the other side remaining in saturated substrate (as opposed to all of them).
IMHO, two things are clear from this.
- tilting the pot 'works' only with shallow pots and is even something one might do after watering such fresh plantings
- tilting becomes meaningless with deep pots, hence a reason nursery and conventional gardening pots are deep