Seems reasonable if we are going with the assumption that they were precise with the wording of the virtue and how if would effect things if in some later book they introduced a method of gaining it. And other such rules interpretations are also equally vague, like how you need a lab total equal to the level of the effect to get any charges when recreating a charged item. This does seem the most logical way to approach it, if you assume precision in the language.
Some people are considering Flawless Magic in the same way as a Magical Focus, in that it is an aspect of the character. If you gained a minor magical focus in Self Transformation, your casting score in spells changing you into a bird would go up, and if you lost it, your casting total would go down.
Some people (myself included) are considering it as a virtue that changes the efficiency of study. If you have Book Learner and you read a book, you get the bonus XP, if you get the virtue later, you don't get extra XP. If you lose the virtue later, you don't lose the bonus XP from books you have read.
Now, if you consider Flawless Magic the same way as a Magical Focus, you take "When you learn a spell" as being too precise of a parsing of the text. There are errors people make by using a too precise parsing of texts. What evidence do you have that this is such a case? What makes you think that the ability gain is from the inherant quality of the caster rather than being something about how they learn magic?
When I look at the mechanics of Flawless Magic make me think it works better as something that adjusts what is learned. It only applies to Formulaic and Ritual Magic, spells which are learned. If is was about how they cast, why not include Spont magic? Magical Foci effect Spont magic. If Flawless Magic gave a heightened understanding when it was gained, why would it give one heightened understanding (mastery ability Quiet Magic) rather than another (Mastery ability Magic Resistance)?