I think some of the confusion around this line may be because of people's understanding of what pseudo means.

The google definition comes up with false, not genuine, sham, resembling or imitating.

Personally I think it's perfectly acceptable, even if a bit silly and far fetched, to say a dolphin resembles a fish in the fact that it has qualities in common with a fish such as fins, a tail, it swims and lives in the water.

If you really wanted then quite a lot of sea life could be called pseudo fish as long as they have similar qualities in common with fish.

But some people see it differently and so I now find the line to be subject to interpretation and actually quite a funny, confusing and diverse topic. As seen in the comments here XD

Once again I've made this too serious but it's fun so I won't change it.