That would potentially be true if they had an MHC role, which they do not. They are to perform the constabulary role.I'd imagine the MHC role would at times result in them being in some form of harms way as they will need to be accompanying or preceding any amphibious force. Of course there will likely be other escorts screening for them but something a little more useful than the 25mm guns could come in handy, if perhaps a hard sell bearing in mind RAN efforts to decrease the number of different gun calibres in use.
There was a proposal that a modified OPV design be used for the mine warfare role, but it has been proceeded with, at least so far as can be determined in the public arena, and nobody outside the people who worked on that know what, and how extensive, those needed modifications might have been. That proposal did not however envision the ships themselves entering mine fields but rather that, as with the new Dutch/Belgian ships, AUVs perform the function while the mothership stood off.