For encryption block looking like this: EB = 00 || BT || PS || 00 || Data
where BT - block type and PS - padding string,
I've read that we use three types of BT - 00, 01, 02. 
Now, since 00 and 01 are for private key operations (where 01 is recommended - why?), like signature, and 02 is for public key operations, like encryption, I am wondering why it is not recommended to use '00' block type. Also, if it is not recommended, why is it even possible?

Apologize once again for being a newbie.