A subject lit with even, full daylight spectrum light will indeed tell you more about the condition of expired, daylight balance film.
But a subject that is lit with even, open sky spectrum light will tell you about the film's response to blue light and other colours exposed to predominantly blue light, and in my experience film that has deteriorated due to age doesn't respond well to those conditions.
So there is something to be learned - and your film seems to have done well.
It was blue in blue light. That is saying something!
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."