Or, is hydraulics simply not a system monitored by ACARS?
When ACARS tells you "probe-failure" it does not tell you, what probe fails. Thats how it works on most airplanes. My humble oppinion.
People are obviously having problems understanding acars. ACARS is a communications system that relays messages. It can be considered as an onboard fax machine and is completely independent of any onboard fault detection system. One of the more useful additional functions is to relay messages from the CFDS system. Therefore ACARS influences nothing. It doesn't decide which fault messages to send, it only sends those that are reported by another system.
So yes it will tell you which probe has failed and it will relay hydraulic, fuel, oxygen and any other message that CFDS has stored. It is also very useful when drivers start telling porkies about faults occuring on a home leg.
Thats why the information is useful and relevant. However it has a few drawbacks too. One good example is AP off. AP off will be reported but you cannot tell if it was a manual disconnect or an automatic one. Although in this case considering the amount of failures it would be reasonable to assume it was automatic but we don't know that.
Any warning that appears on the ECAM system will be stored in CFDS and if the acars option is in use that warning will be sent back to base.