My understanding is that returning claims was intended to allow players to correct for misclicks after immediate claims were implemented. Given the relatively lax restrictions on when claims can be returned, however, the feature can be used for a variety of things that it maybe shouldn't be possible to use it for.
1. Adjusting claims post-auction: I'm mostly fine with the idea that you can refund a claim if an auction comes up that makes the claim redundant, but Pbhead does suggest in his cast of my first round match vs TheSpinCycle that me canceling a geo after a geo auction was "not okay." To some extent, having the claim down but unbuilt does impose an opportunity cost on the claiming player, but being able to change the decision after getting more information can be an additional advantage that may be unnecessary.
2. Escaping black market: It seems very broken that you can return frozen claims, then move them to a spot that isn't frozen (the spot does keep the frozen status if you return and reclaim the same spot). At the very least, claims shouldn't be able to be returned until the freeze has lapsed. To be fair, you can avoid this problem by waiting for buildings to complete first, but that's both suboptimal and another level of tedious micromanagement. This feels different from scrapping from frozen tiles and building in a different spot, as that does at least displace something else (though both situations do reset construction times).
3. Temporarily grabbing resources you never intend to use: Basically, you might claim resources just to get in the way of your opponent, then refund them once his claims can no longer be returned. I have a hard time seeing this being overly advantageous in most cases, but it does seem like an annoying thing to be able to do.
A time limit on how long you have to return a claim is probably appropriate to avoid these and other (likely) unintended uses, even though I do like the flexibility granted by being able to change your mind under the current circumstances. Mostly the frozen tiles thing is what I'd like to see adjusted.
