MS Office Instant decryption

Hello,

I wonder how some tools (Passware for example) claim our their website to "instant decrypt" Office files version <2003 40-bit encryption.

Then I saw their secret - I guess - which is "Decryptum Portable : a set of rainbow tables that allow instant decryption of Word and Excel files up to v.2003 with a Rainbow Tables".

What do you think about that ?
Would it possible to implement this kind of attack in hashcat for old Office hashes ?
Once one have the rainbow tables I guess the attack will be hugely fast ?

Thank you for your advices