Modern plumbing makes no sense

Near the very beginning of this movie, we hear a toilet flush. A modern, familiar-sounding toilet flush.

This happens in a wooden.. I don't know what you call those things in english, but the point is, such primitive wooden structures in the middle of the forest would NOT have plumbing whatsoever! (Believe me, I have used plenty of those, they are disgusting)

Not to mention this is set in some 'olden era', with castles, knights, dragons and whatnot. Even the king's castle wouldn't have plumbing, let alone some troll's primitive wooden toilet in the middle of the woods (or middle of nowhere).

Now, this is a 'fantasy world', of course, and there are things like magic mirrors that function as a modern television, magical creatures capable of summoning all kinds of things, magic pixie dust to make donkies fly and so on, so maybe this observation is completely worthless, perhaps plumbing can exist side by side with the 'olden' world.

After all, they have 'voice recordings/captures' and some sort of animatronics as well.

However, this brings another problem - if the world is advanced enough to have plumbing, shouldn't it be at least advanced enough to have OTHER similar-level technologies, like cars, airplanes, etc.?

It's like they picked a couple of 'modern conveniences' from the modern times, but then did not raise anything else to that level. That's NOT how anything works. Either the world has invented plumbing, electricity, cars and such, or it can't have plumbing.

Of course in these 'imaginary fantasy worlds', you can say that anything is possible. But why would that 'anything' be so incongruent? It makes no sense.