It has nothing to do with the gateway, it is a parameter specified by the ISP, this is an error correction protocol.
When a customer is put on a "Noise Profile" usually their DSL line is changed from FastPath to Interleaved.
Interleaving is an error correction protocol that is implemented for your line at the DSLAM. With Interleaving enabled, the DSLAM can correct errors in the data stream it receives before passing that data to your gateway router. It is usually implemented on noisy or marginal lines and can greatly increase sync stability and effectively eliminate "first hop" packet loss. The largest drawback to Interleaving is that it will increase your ping time, specifically to your first hop gateway router.
Your best bet it to contact IDM by mail since they are less likely to lie or try to beat around the bushes, you should get a straight answer by mail. Also tell them all the ISPs are doing this for their customers upon request (Ogero is doing it for sure as I am subscribed with them and I requested it long time ago, they done it the same day), keep annoying them until they do it.