IIT Hyderabad has the best reputation of being highly ranked despite being a second-generation IIT. However, it’s a misconception that IIT Hyderabad has a unique double major system when in reality the double major system is being followed by IIT Bombay or IIT Kanpur way before IIT Hyderabad was even established. Both these IITs follow this system to date. IIT Gandhinagar too follows a system of minor programs and their own version of less credit diverse courses. There are many other IITs that have double majors options apart from these 3. So, no, IIT Hyderabad is not the only IIT with a double major system.
The only thing it’s unique in is its fast-paced development despite being a new IIT.