Problem is, it doesn’t do what you think. You need the router to use the right resolver (i.e. not ISP’s) and client to use router (default is 192.168.88.1; you can have different config) as resolver. What actually happens is that when client gets 192.168.88.1 and tries to use it, dstnat forwards all client’s queries to 208.67.222.222:5353, so it completely bypasses router as resolver. But the router itself still uses whatever it has in “/ip dns” (so ultimately always ISP’s resolver), because dstnat does not apply to router’s own output.
There’s the ugly hack I mentioned before that can help with that. It really isn’t nice, but as a desperate solution it can work.