Yes it does not see which side is blocked, but that aint no problem. even if you hit the hole with a tap and nothing comes out because it blocked. just remove the leaves around and the previously generated resin will fall down.
Je, i will recode this effect slightly, causing the resin to always pop out on players side, shouldbe possible.
This effect is related to leaves not being considered blocks (as their are transparent). Thus items attempt to "fall" through the leaves, getting stuck in them.
Another small rubber tree bug, leaves from other rubber trees (possibly all trees) stop the growing of the tree, resulting in very short rubber trees. I observed two and even one log short trees.
Picture attached
Another small rubber tree bug, leaves from other rubber trees (possibly all trees) stop the growing of the tree, resulting in very short rubber trees. I observed two and even one log short trees.
Picture attached
Looks like a bug in the algorithm for tree growing, could this pertain to the fact that leaves aren't considered blocks?
Rubber trees grow according to the space you give them :3 sizes below 4 can only occur if you block their growth, but yes, they are possible.
So no tightly packed rubber tree farms? 
Just thought this is a bug because its possible with other trees, since they just grow through leaves.
edit:
just found another rubber tree mini bug: punching it gathers exactly as fast as with a stone axe(only axe i tested).
You can pack your rubber trees tightly if you remove all the leaves above the sapling before it grows - it can only grow up through empty air.
Axes will harvest rubber trees quite a bit more quickly in the next release, as MC Forge has allowed us to register them as effective.
