Mycorrhiza are ubiquitous in the landscape, and forests where maples come from. Spores are everywhere in the air. Documenting mycorrhizal relationships is difficult to meet peer reviewed journal standards. So just because mycorrhiza relationships with maple have not been documented, does not mean they do not form. The relationships may not be obligate, but rather opportunistic. In container horticulture, species that are "easy to grow in pots" often are species where the relationship with mycorrhiza is believed to be optional, not obligate. But for most trees, it is believed that in the right conditions for the fungi, and the "right species" of fungi present, these relationships can form.
So, does using Rhizotonic make you feel better about your trees? If yes, then keep using it. It won't hurt. It may not do anything, but it won't hurt. And if your care is consistent, and the environment in your pot is favorable for mycorrhizal fungi to develop, perhaps your tree will get lucky.
Note pines use ecto-mycorrhizal species, these form visible to human eye mats or webs of mycelium. Oaks also. Other deciduous trees, or a shrub I know about blueberries. (family owns a blueberry farm) the favored mycorrhiza is endo-mycorrhizal, the main body of the fungus resides inside the cells of the roots. The mycelial webs from endo-mycorrhiza are very fine, rarely visible to the human eye without optical lenses. So there may be relationships that one simply does not notice.
So I do not know if maples form mycorrhizal relationships or not. So use of these "magic elixirs" to encourage mycorrhizal growth, may, or may not be of benefit. Who knows? If they cause no harm, no reason to not use them if you feel they help. It is fairly certain, that under some favorable conditions, maples may develop mycorrhizal relationships. But as far as I can tell the "science" isn't there yet to say one way or another.
