That's the entire point. The crypto is not very good. Also it doesn't apply to all bluetooth keyboards because Microsoft uses a proprietary protocol to communicate apparently (at least this series of keyboards).
Hold my beer while I perform a table flip and throw away all my Microsoft Wireless Keyboards
I'm unsure if Logitech keyboard are affected in a similar way, I know that this attack only affects Microsoft keyboards but they may have similar issues.
[1] http://www.logitech.com/images/pdf/roem/Logitech_Adv_24_Ghz_...
https://penturalabs.wordpress.com/2013/09/04/bluetooth-sniff...
https://penturalabs.wordpress.com/2014/02/20/ubertooth-updat...
As far as I can tell, bluetoooth keyboards should be a bit better off. Not sure how the "secure" modes work (presumably some kind of DH-exchange?) - but apparently they're not immune to brute forcing.