They’re going generic because they don’t know yet which one Obama will side with.
Look at his recent speeches and the implicit respect he accords them and the formal way he speaks about them.
Obama is paving the way to formally recognize ISIL as the legitimate government of a legitimate new Arab state, the Caliphate of the Levant.
Referring to ISIL as a terrorist organization would complicate that recognition.
If Obama’s boys in Syria could not overthrow Assad and take over Syria as ISIS, they can seize poorly defended desert lands in Syria, Iraq, Jordan and Lebanon and become ISIL to start their own country.