Why would RQ be able to summon her shield but not her sword? One is inherent to her Gem, the other is a physical item. There is clearly some special property to summoned weapons, and this is shown during fusions where the physical forms of the weapons themselves are modified to make new ones.
Bismuth might have made Ruby's gauntlet. It's interesting that Ruby has only one, while Garnet has two, though. which is why I think it's an inherent weapon she was made with that is encoded in her Gem. It's also possible that Ruby was simply never taught how to summon her weapon, because no one thought that Rubies had inherent Gem weapons (if such a thing exists). Similar to how Peridot didn't know she could metalbend; she'd never tried before, and clearly no one had entertained that thought in her mind. She DID, however, try to shapeshift before, even though as an Era 2 Gem, it might not always be considered possible.
So is the metalbending something Era 1 Peridots could do? Or is it something to unique to our Peridot, like a Gem weapon, that a Gem has to discover for themselves. But again, if they were never told it was even possible, they might never try.