I think how my WAMU portfolio is currently laid out supports what you are saying, in the way that the P's are being kept separate from the former K's and U's. I have as follows: WAMEC (X) where 'X' = the number of old WAMUQ shares. WASH (Y) where 'Y' = the number of old WAMKQ shares. WAMPQ.C1 has the number of old WAMPQ shares. I believe WAMPQ was '.C3' and '.C2' before this.
For some reason they are separating the P's from even the K's, which are also preferreds.