Sounds like they use a relatively low to medium fees to transfer your balance. That is not wrong at all, but you might find some trouble if the network suddenly got congested. Can you do an RBF with this wallet?
And a gap of 2 hours to broadcast the tx is too long since this should be instant if you have full control of the (bitlum) wallet.
So, is it an exchange-like service which implements "transaction batching" to withdrawals;
Does the txid of those two transactions involves multiple outputs or just yours alone?
If it indeed works like that, I don't see any relevance on using LN for those purposes. But it could work as a "reloadable micro-wallet" for small transactions utilizing lightning channels.