This is probably intentional because: The first text shows the block ID (for example: minecraft:furnace) and the metadata or data value (for example: the orientation of the furnace) whereas the second text shows just the data value and makes it easier to find it. This part of the F3 is meant to be used by modders and for the API.
also me. i think is to all.
Confirmed for 14w31a
May have to do with the item stacking mechanichs, not sure though
I have tried it in 5 worlds and in all of them the bug could be reproduced.
This is probably intentional because:
The first text shows the block ID (for example: minecraft:furnace) and the metadata or data value (for example: the orientation of the furnace) whereas the second text shows just the data value and makes it easier to find it. This part of the F3 is meant to be used by modders and for the API.
I do think it works as intended
Updated to a most detailed explanation.
Fixed in the latest Snapshot 14W28B