I think they behave a little differently.
A true lipoma can not pass in and out of the deep rings it is fixed to the spermatic cord. It also has a beginning and end point and will not increase in size during straining.
The retroperitoneal fat and patent process vaginalis is what I refer to as a pre-peritoneal fat tongue and you see these from time to time.
A pre peritoneal fat tongue does enter the canal through the deep ring (patent process vaginalis). It is usually a thin slither of fat and it pokes into the proximal end of the canal when straining and then disappears back through the deep ring during relaxation. It does not distend the deep ring much at all ( a true indirect hernia DOES distend the deep ring as the head of the hernia passes through it) and hence the lack of distention means little or no pain is caused by it. The movement of the pre peritoneal fat tongue is often rapid as it slides through the deep ring into the proximal canal and back again.
I think of it as an ant eaters tongue poking into the ants nest, grabbing an ant and then retreating quickly!
Steve