I will try to follow the argument here:
You use the sentence: "Here are new and modified Supernatural Abilities, Virtues and Flaws that characters can choose from when designing magic characters or characters that are somehow associated with the realm of Magic." as an argument to link characters associated with Magic and Magic Might.
Ok, but if i work under that assumption, I find that, as i said, virtues like Focus Power, Greater Immunity (Deprivation) and others doesn't have any sense and should be deleted (i you have Magic Might already, you don't really need those after all).
Others would be unpickable, like Transformed (Being) needing Might to be able to have Might in first place.
And don't forget that the sentence tells you that all the abilities/virtues/flaws listed there (both new and changed) are for characters associated to the Magic. So, by that logic you would also need Magic Might to pick Ferocity, Magical Mount, Small Frame or Environmental Sensitivity.
Idk, i feel it weird. This way to interpret the rules make way more holes than it covers...
I would note that Essential VirtueFlaw and their associated Essential Trait is presented as a bit more stringent than just being related to magic. It represents the fact that you are so strongly associated with the realm of Magic that you share its unchanging nature. So much so that it makes it difficult for you to develop, increase or decrease Personality Traits (as stated on p.54)... much in the same way that it is hard for a magical being to increase their abilities.
You add that Essential Virtue/Flaw are somewhat more attached to the Magic Realm that others virtues.
More than Monstrous Blood? Or Magical Master? Idk Arthur... here we would just enter into a subjective discussion, and that would not bring any light.
I would also like to note that when the rules want to restrict some virtue/defect to some characters, it tells us explicitly. We have several examples at the very same RoP:Magic list:
Magical Champion
Minor, Social Status
Only characters designed using the rules for Magic Character Creation may take this Virtue.
A small group of individuals considers the character to be their particular representative, by virtue of its ma.....
Blatant Magical Air
Major, Supernatural
Only characters with a Magical Air or The Gift may take this Flaw.
The character is especially disturbing......
I know that there are a few errors into that book, but i'm sure that, if per RAW they wanted to restrict any of those virtures/flaws into having Magic Might, it would be written.
If you want to houserule it like that its ok But I will point out that ruling will arise more issues that will need further explanations for each case.