Okay if its optional then this is not a “problem”.
Hans Moog

It is not true for any DLT if you take the asynchronous nature into account. Especially for DAGs it is a major task to check that the referenced transactions do not contradict each other, leading to a conflict.

In lattice, it is far easier to check: If a parent transaction on the chain is referenced by more than two child transactions, you can be damn sure that something is fishy. Without walks, without complex checks. Straight away upon receiving the second child transaction.

Then, the realm’s nodes can react. How? Depends. The default is that the consensus kicks in and everyone agrees on one of the transactions. Through extensions, the nodes might have another logic and simply ban that account for good.

Same applies for transaction selection. There is no resource intensive GTTA: you always know what transactions you need to reference. Do you imagine the performance boost in high load environment only because of this?