But here is the answer (i think, correct me if i'm wrong).

If you incubated your cakes one direction, you should leave them that direction in the fruiting chamber. Pins and mushrooms will for the most part form on the top.

However, if you flipped them over when you put them in the fruiting chamber, the pins will form and try to grow underneath the cake (this happened to me).

Because of this some people will incubate their jars 'upside down' so that they can birth them and keep them that way with the vermiculite down. I guess gravity does play some role in the mycelium's determination of where to pin. But whatever way they were incubated, keep them that way in the fruiting chamber (even if they seem to be upside down).

Note: If you are casing this really doesn't matter cause you will crumble your cakes anyway.

So I believe the shrooms growing from the bottom has to do with something besides how the cakes are colonized, and see no reason that they can't be fruited upside or rightside down.

Perhaps it has more to do with the water settling at the bottom of the cake after being fruited, or the top drying out from heat.

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I think the monkeys at the zoo should have to wear sunglasses so they can't hypnotize you.

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Trying to rationalize with an irrational person, is in itself irrational!