...the object is often to depict the whole system, as far as can be known, on one page. Admittedly, it was in another branch of the mapping genre (cause mapping, a.k.a. influence diagrams) for which this was stated by the Prof who had led the field, when I was facilitating on an elective course he taught. It would undoubtedly get the same reaction from Graham.
Anyone that can manipulate a mind map at all, i.e. if it is presented in "clickable" form, say exported from MindManager® for that purpose to Mindjet® Player or uploaded on Mindjet® Catalyst, can shut down a lot of detail so that it cannot be seen and read till opened up again, and I suggest this as a means of overcoming the disadvantage as Graham sees it.