Which doesn’t necessarily mean they are either right or wrong.We claimed back in 2014 that Russian IRBMs had violated the treaty prohibiting missiles with ranges of 500-5500 kilometers. A 1250 kilometer range - especially if fired at altitude - would not be all that surprising. The basic ground launched version carried a nominal 490 km range for a one ton warhead. A less accurate export version was determined to have a 300 kilometer angle.

Iskander (SS-26 Stone) Short-Range Ballistic Missile | Military-Today.com