Flowering oak saplings never grow, either naturally (~20 hours gameplay with several flowering oak saplings in loaded chunks, none grew) or with bonemeal / 3rd-party "fertilizers" like the OpenBlocks watering can. Apple tree saplings produce apple trees with persimmons in place of apples. Tested with and without other mods.

I definitely experience this as well. Also, pear and peach trees do not seem to have sapling variants.

Flowering Oak sapling wasn't fully implemented. This is why it never grows.