May be a feature request, especially since this has been the case for years, however it's still logically inconsistent so reporting anyway. Note also that a large portion of reports tagged with placement-and-support have been considered valid.
Bamboo can be placed on sand and gravel. This makes it inconsistent with the majority of other plant blocks such as flowers, grass and saplings, which are restricted to planting on dirt-related blocks. Expected would be either (undesirable solution) for bamboo to not be placeable on sand and gravel, or (preferable solution) for other plants to be able to be supported by sand and gravel due to their dirt-like granular nature and ability to generate on top of them naturally.
This could be fixed by perhaps adding a block tag to control what plants can be put on, containing, #dirt, #sand and gravel, which would be used for most blocks. #bamboo_plantable_on would be defined with this tag and also include bamboo blocks.