This all gets back to being "suitable". If something from a responsible company is sold as wire lube, it is probably suitable. When you start using something sold as something else, you are on dangerous ground because it may not be suitable.
The reality is, wire like THHN is pretty tough stuff and not easy to hurt but dollar for dollar, why take a chance on something that probably costs as much as the real thing?
Good old "77" really seems to work as well as any home remedy.
As a side note, if you are pulling CAT5 or coax through smurf or RNC a little squirt of 77 makes the difference between getting it through or not. That stuff will seize up in the raceway in a heartbeat without some lube.
