You’re bringing up the “most important question” I will agree is a commendable effort to bring up eternal awareness’s. But this still isn’t reason to detract from Paul’s comment “her glory” and instead to imply he really meant “care less”.
1 Corinthians 11:15 is not referring to the heads that are uncovered or covered in 1 Corinthians 11:3. Regarding hair in this context, Paul could care less. 1 Corinthians 11:6 is indicating that if a woman is not covered then let her also be shorn or shaved. Again, the only caution, if it be a shame, let her be covered. Not the same covering to the head as described in 1 Corinthians 11:3. Paul could care less about hair. Hair is not a requirement to be saved. Hair is not a requirement to serve God. Without faith it is impossible to please God. Hair is not the issue with the heads of 1 Corinthians 11:3

1 Corinthians 11:15 is a clear statement that means what it says. It is used with the rest of the verses to demonstrate what it means for a woman to cover her man/husband in the context of verses 3 and 5

1 Corinthians 11:15 But if a woman have long hair, it is a glory to her: for her hair is given her for a covering.

1 Corinthians 11:3 But I would have you know, that the head of every man is Christ; and the head of the woman is the man; and the head of Christ is God.

1 Corinthians 11:5 But every woman that prayeth or prophesieth with her head uncovered dishonoureth her head: for that is even all one as if she were shaven.
1 Corinthians 11:6 For if the woman be not covered, let her also be shorn: but if it be a shame for a woman to be shorn or shaven, let her be covered.