You mean how close to spawning they are?
I agree if you mean after you start supporting them (minimum 1 month) but not before.
I agree that there should be some possibility to check the progress of rebels you support.
Imagine you were looking through a country that has 10 different rebel parties trying to rebel. It'd be very annoying to send and retract your diplomat for a year just to find a suitable target group to support, if you had to support a party for a month to get the progress report.
Maybe reveal the progress of ALL of the country's rebel parties after a month?
Or maybe allow the espionage option "infiltrate administration" to show rebel progress?