I guess I cheated.. I have tried poly before did not seem to last. When I ran the last pipe in the woods 3 years ago used Flexible PVC. It uses the same glue on fittings but for the most part as I wound around the woods and made several turns never needed to add a fitting!!
I have no doubt it works for PVC conduit in those sizes. Its a softer material than SC40 pipe. Its the larger diameter SC40 PVC that I doubt works, and if you look at their video, they don't show the pipe once its bent, or indeed a 90* bend which they claim.
I've personally used a similar device to bend PVC SCh80 CPVC sch 80 up to 4" using one of these. the main key is to cap the ends so that the air pressure as it heats up maintains the diameter both inside and outside. when you buy these they come with rubber plugs that you slide into the ends to plug the pipe and keep air in. we bend the pipe using many things the most popular is floor cracks to keep the 90. you need to slightly over-bend the pipe at first and as it cools then let it spring back into place. I'm not familiar with the other devices that people are talking about. a modified gas grill might work OK but the flame may cause some issues as the electric ones dont get extremely hot and have a pretty stable temperature. the pipe will sag but not all that bad you have to keep eye on it to make sure how flexible it gets. use mop or rags in water to cool it once it is placed/bend.
Pack the section with sand and heat and bend. The sand will not allow the area to collapse and can be dumped out after the bend is made. An old timer told/showed me this trick only we used copper.