In the first one the question word is replaced with the referent asked about without disturbing the word order:
Whose book won the prize?
His book won the prize.
The other question has a completely different structure. Here we have a linking be, so factors relevant for this construction are in play. The answer will involve a reversal of the subject and complement:
Whose gloves are these?
These are my gloves.
The subject and the complement swapped the places in the answer - instead of simply supplying "my" and saying "My gloves are these" the order has to be reversed too: "These are my gloves". This is where the sense of inversion comes from.
"My gloves are these" is a perfectly formed sentence, but it is not a possible answer to the question. (or more precisely, it would be a very unlikely reading. One would need to be extremely proud of his gloves and also very melodramatic sounding to put it that way.) The question asks not to point to a specific pair of gloves, but rather to tell something about them. (who they belong to).
In general, reversing the positions of the subject and complement in the ascriptive linking construction is possible but not all that common.
"These" is a demonstrative and it obviously cannot be understood as ascribing a property to the subject "My gloves". Of course, if we replace "these" with an adjective, no role reversal in the answer will occur:
Whose gloves are the warmest?
My gloves are the warmest.
The expected and natural order in the ascriptive construction is : subject - property ascribed to the subject. "My gloves - warmest" fits the ascriptive pattern, "My gloves - these" doesn't. "These - my gloves" does.
If the question is asking to specify the subject, no reversal of roles will be required either:
Which gloves are yours?
These gloves are mine.
The question determines the kind of interpretation that the answer will receive. In writing, the sentence "These gloves are mine" in isolation can be interpreted in two ways. When spoken, the sentence stress will suggest the appropriate interpretation.