6.0 marshmallow - Data recovery from encrypted phone based on glitches in the encryption?

To make a long story short I needed to root my phone and didn't notice the warning that unlocking the bootloader erased all contents of the memory.

I contacted a data recovery company and told them that the memory was encrypted and the phone used Android 6. In response I was told that there was a chance, albeit small, that they could recover some data. However, they were unsuccessful and in their report they blamed the encryption.

This made me pretty upset since the encryption was the first thing I mentioned in my contact with them. When I called and complained about this I got the very "interesting" answer: sometimes there is a glitch when enabling encryption leaving some of the storage unencrypted and we might be able to recover that.

Is this really true??? It sounds completely absurd that something like that could happen frequent enough so they could base their business model on it. In my ears it sounds like a bad excuse for charging me money for something that could "never" work.