You are correct in saying that the Top XX Netflow Sources by % utilization is indeed limited to 100. You can put in a feature request have to this increased. Post back here when you done and I'll vote it up.
But in the meantime if you can add a key word to the interface description of each Netflow interface such as the word netflow, then you can use the Top XX Interfaces by Percent Utilization report as this report can have more than 100 interfaces listed. Then all you do is add in filter such as fullname like '%netflow%' and all those interfaces with netflow in the description will appear in your view.
can the 100% limit be removed?
in a switch, one can have over-subscription. depending on the case, this can be fine
if there is a lot of the traffic stays inside a L3 switch it does not matter that the some exceeds any one links