You misunderstand. It's not the use of orbital rockets for ICBMs (which is really not hard to do, btw); it's one of technological capabilities in regard to rocket performance.
Iran doesn't have missiles with sufficient performance (i.e., range) to hit Israel.
Israel, OTOH, knows how to make rockets with orbital capability, which says they don't have the missile performance issues that Iran does. Range is not a problem for them -- they can hit Iran.
BTW -- did you know that the only thing separating a ICBM from an orbital rocket is that the latter has an upper stage, and the former does not? Both we and the Russians have successfully converted ICBMs for orbital use.