bootstrap.dat is unpacked, sorry if i got you confused there. The problem is bitcoin-qt acts as if it wasn't there.
Bitcoin core does recognize the bootstrap but it needs to index all of it so it will appear as if it is syncing from scratch.
Wont be faster to sync from bootstrap.dat? Even if I'm using a Raspberry Pi?
No it wont, the limiting factor for your RasPi is the CPU. Whether it reads the data from disk/sd or internet does not matter. In fact the bootstrap.dat slows you down, because you first download >60GB of data and later verify it, instead of doing both at the same time (regular sync).
What you can do however is sync the blockchain on a different (besides windows if you are using > 0.12 due to the obfuscation) machine and copy the entire data directory to the RasPi.