Though I'd argue the risk has kind of always lied there given companies can ship updates to phones. You could maybe argue it'd be harder to legally compel them to do so, but I'm not sure there's much to that.
The modern 'megacorp' centralized software and distribution we have is dependent on policy for the most part.
It does have some advantages - it's easier to argue (see: the disaster that is most of the commentary on this issue).
It also could in theory be easier to argue in court. In the San Bernardino case - it's easier for Apple to decline to assist if assisting requires them to build functionality rather than just grant access.
If the hash detection functionality already exists and a government demands Apple use it for something other than CSAM it may be harder for them to refuse since they can no longer make the argument that they can't currently do it (and can't be compelled to build it).
That said - I think this is mostly just policy all the way down.
Given the amount of nuance here, I also think it's important to differentiate between the FBI showing up and asking for something and government passing laws forcing encryption backdoors. The former is what Apple has fought to date b/c they can. The later is much harder to fight and Apple will most likely have to comply regardless of what features already exist or not (see China/iCloud). The later is also the most dangerous since politicians rarely understand technology enough to do something sensible. It remains to be seen, but Apple could be trying to get in front of long term law changes with an alternate solution.