Isn't it rather simpler? The RCR now governs the UK market; there is no longer the RCD (for the UK) and therefore no "new Directive".
Moving on (less certainly...) the requirement for a PCA is in regulation 43 which only relates to private importers or where a Major Engine modification or Major Craft Conversion. Both of these Majors are reasonably well defined - with the latter including something that does not meet the Essential Requirements. And the Essential Requirements make no specific mention of (purely for example) multiple negative connections to battery posts, inspection hatches to fuel tanks or return wires to horns.
So if a broker notes that someone has breached the Essential Requirements by (for example) unbolting the anchor strong point, it requires a PCA. More practically, if the owner replaces the strong point and takes his vessel to the next broker, it is difficult to see how the second broker is going to know that it was missing for a while.
I am not claiming this makes it OK, but the moral would seem to be to ensure your boat gives your chosen broker no real reason to think it does not meet (nor has not ever met) the Essential Requirements. I don't see the broker has a duty to check everything in minute detail - just not to ignore a clear breach. Short of the broker arranging a PCA itself, it's hard to see how it can work otherwise.