The two inputs for the flowTOP are just named Input 0 and Input 1 without clear indication of what the are doing.
Doing a little research and testing it seems like Input 1 is a depthMAP to hide parts of the flow, and Input 0 is used to merge a renderOutput with the flow.
This is not (at least not clearly) documented. Simple Update to
Render Input
Depth Map would be much more clear.
In the operator help pages there is a “inputs” section after the parameter page help and before the Info CHOP help. This was added within the last year or so and we’re trying to fill this for all nodes.
But the actual inputs on the node would be nice to have named, have added that RFE.
You had me guess ma sanity here for a moment as I was sure that this was not there before. And in fact, @snaut updated the wiki yestertday 
Ah – and I didn’t hit send on my response in the forum before leaving the office…
Sorry about that
Best
Markus
Haha, comedy of errors there, but glad we are all on same page now!