Yes, I am not expert in networking but we need not an expert opinion in the real life, even we have other members including
@Siva and others who owns devices which do not support MU MIMO but gives full speed.
You need to interpret and do not take get incorrect ideas while reading any article.
Also MU MIMO router works when the other device to which it connects also has MU MIMO support.
There is no doubt that MU MIMO is better technology.