I agree. No need to use ICBMs with over 10,000 km range.
Russia's Medium Range Ballistic Missiles already has a range of 2,000 km.
Their Short Range Ballistic Missiles can reach up to 550 km.
In comparision, the ATACMS provided to Ukraine has a range of 300 km.
While Ukraine can identify if it was a ballistic missile fired at them, I suspect maybe there was some miscommunication. Military top brass told president that is was a ballistic missile, then president thought it must be ICBM.
Of course, it is also possibke that they intentionally said ICBM, since this would cause more fear. "Russia is attacking me, he can attack all of you as well since you all are within striking distance".