Just for your info, I recently consolidated all of my escrow markers that are scattered in 3 accounts into one. All accounts are from TDA but that is irrelevant.
As for my WMIH shares, I lost track of which shares came from my old converted P and which shares did I buy recently. TDA came up with a cost basis for those shares for my tax purpose. I used it for filing my tax just for convenience and it is advantageous for me to use, because the cost basis they calculate is rather high. If I get audited by the IRS then I just say that is what TDA calculates for me.
You give too much credence to your 2 cents broker and here is potentially millions of dollars that you trust them to handle it properly.