Yes, this is true. I did notice that a bunch of channels I knew I had blocked started showing up again, but in my case it took 2-3 years. If it only lasts months for you, it's much less useful.
To be fair, it is entirely possible it works better today, than it did then. I was just so aggrivated at the time, thinking each time I had resolved it, only for it to appear again that I just gave up!
