I also figure the Hierarchy works on discovery too - if a Probe logs something interesting but weird according to it's parameters, it can squirt a messgae back to it's 'boss' survey ship, which can amble over and have a look with better facilities and more sensors, just to rule out false alarms etc. Also to restore it's stocks of material if a Probe spots a good location for easy Extraction. Hence why some systems will have Probes and a Survey/Mothership: sometimes a Probe called the other ship over for some reason...
Basically to avoid the Niven Ramrobot problem where the Probe reports something, you send a colony slowboat (or in this case, a Domain Cryosleeper...), and when you get there on your one-way trip, you find out the Probe was acting Janky. (For those not getting the reference, in Larry Niven's Known Space setting, the Ramrobots had a programming oversight that meant they were searching for a Habitable Point rather than a Habitable Planet, therefore on arrival at a system, they'd fly round endlessly looking for any single point that matched their criteria, then signal success. This lead to things like settling the inner planet of Tau Ceti, which was mostly like Venus, except for one Mountain plateau sticking up out of the clouds...)