The item data values for wood seems to be wrong, for some reason when trying to give yourself a block of wood with the data value of 6 and 7, it gives you a regular oak wood/bark block. I'm assuming it considers it an invalid value and defaults it to 0 as it does when you get the value wrong. Is this a bug or is there a reason that 6 and 7 are skipped and it just starts at 8.
I've noticed this error since 1.16.10.
If you need it, the commands are:
/give @s wood 1 6
/give @s wood 1 7
and it defaults to
/give @s wood 1 0
for some reason.