>>Staked tokens are locked in a smart contract deployed on the Ethereum blockchain. Validators do not hold the actual custody of the tokens delegated to them.
for no reason in particular except for shits and giggles in the best case, incompetence because their blockchain wasn't ready yet and they never could change the staking model afterwards in the worst case
the distinction people care about is whether transaction finality depends on Ethereum or not. it doesn't.
validators merely activate their status as a node by doing a random assortment of things, which in this case happens to include moving assets on the Ethereum network. that's it.
Source:
https://kriptomat.io/polygon/
>>Where do staked tokens reside?
>>Staked tokens are locked in a smart contract deployed on the Ethereum blockchain. Validators do not hold the actual custody of the tokens delegated to them.