When a block with NBT tags is placed, it actually loses the tags. I've attached a tag to a redstone lamp saying that it can only be placed on obsidian. This tag WORKS, it won't place on any block but obsidian. However, I've mined the block with a pickaxe (set with a tag that can break redstone lamps) and I got the lamp back, but since it lost it's CanPlaceOn tag, it can't be placed anymore.
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It's because placed blocks aren't meant to store data. Only TileEntities store metadata like this, it would be too expensive for regular blocks to do so as well.
This bug still isn't resolved. I still have the issue. Why is it closed?