I think its like youre saying, the way they process the submarine swaps with micro utxo sets on chain do something with fee rates with larger amounts of sats on LN and on chain.
Although I'm not technically equipped enough to fully understand what's going on.
I wouldn't call it stealing or unsafe to store sats on, just... something more complicated going on behind the scenes to make it as easy as possible for the user.
Trade offs.
