Not necessarily true!
I've noticed that the other two Chinese forums do not teach you Chinese.
In the other Chinese forums, it only has people chatting in Chinese and simply translating what they said.
I haven't seen anyone say anything about how to read, write, or say Chinese.
However, in this forum, Miwako-chan talks a little bit about how to read, write, and say Chinese. She also provides some helpful links.
Thus, I think the idea of this forum is most helpful out of all three because it actually helps people who don't know anything about the Chinese language learn it a bit.