If you read somone stuff on Mando armor, its isn't always made of Mandalorian Iron (the sandard stuff). It's either that or the next best thing. The fact is, Mando Iron is expensive to make/get, which adds to why Mando armor is so well prized.
It's still possible that a Clone decided to make a new set of armor based on the clone armor since he's used to it so much, and decided to mix the best traits of both. He could have possibly even scavanged some parts from his original armor. Who knows, maybe he set a theme, and the new Mandos led by Boba start to use their own version of it