I suspect there has to be some semblance of support. Maybe not at the funding stage, but looking at what a big Ocean you have - and the desires to be involved in both Atlantic and Pacific - the CDC/LF platform allows (or appears to from my non nautical experience) to offer the GoC another Warship that doesn't have the bill of the River class Destroyers, and allows for the ability to put something somewhere that a River is not needed.
You don't want to have your Sub fleet being all visible over the map - and the 15 Rivers are not just a ways out, but looking at how hard the Halifax's got ridden, the idea of a 2nd Tier Combatant has to be attractive to many (and not just Senior RCN folks who can command more ships)
It appears you are sending AOPS into the Caribbean, and other places where they to me are better suited for the northern oceans.