Ethereum

When people say that stablecoins like circle and tether are going to be able to control which chain is canon in the event of an L1 chain split, why isn't it possible to only allow 1 chain to access the "shared" coins, but have that up to the user?

Since this is all backed by tether/circle having USD equivalents, it's not important where the coins "are" and so i don't understand why circle/tether have to pick a side in a chain split. 1usd = 1usd regardless of where.

After claiming coins on 1 chain, the other chains coins in the token contract against your address are burned. You could even claim 50% of your coins on one chain and 50% on the other.

Something like a 2 epoch (or until a chain is final) period where you can't finalize a transfer, but it's pending & if you're trying to access both chains coins at once, then it all reverts? You could make this a "claim period" so people have to claim USDC/T out of their respective contracts before doing anything else.