The pick list of event data strips the cluster, only allowing access to the elements inside the cluster. In order to manipulate the native datatype, you must reconstitute the cluster inside the event structure, a performance hit on large data structures firing at quick event rates. This is not to mention a messy FP.
I suggest that User Events preserve the clustered event datatype, allowing the programmer to access to the native datatype on the consumer end. The option to select only the element "Clustered Typedef.Array of I32s" of course still remains, but is not forced upon you. (Note that the below block diagram is NOT a direct LabVIEW screenshot... brought to you by trickery and a paint program. I clustered the cluster on event datatype [not shown] so that the event structure could eat the outer layer)