Mixing Indian cultures has been standard in Playmobil from the beginning. It is a result of German Karl May-ism, in other words a romanticisation of the Indians by a culture with no real experience of them. Things get jumbled together in the imagination and striking elements are combined to heighten the power of the image. You can see totem poles next to wigwams in several of the films based on May:
(see upper right corner of that last picture)
What this means is that Playmobil Indians aren't a representation of real Indians, they are a representation of
Indians as they appear in the German popular imagination.
I think this is a point worth emphasizing in discussions of representation in toys etc. of the sort we have around here from time to time. PM Indians are incorrect with respect to reality, but they are not wrong
per se - they are in fact doing exactly what they were designed to do: express the German imagining of Indians. Depicting a culture's image of another culture is just as "real" as depicting that culture directly; it's a real depiction of that image, not of that other culture. That image might need updating or what have you but if so it must be addressed at that level.
Coincidentally I was recently looking through a book of Pacific Northwest Indian art - lots of lovely totem poles among other things - and there are a few sculptures depicting Europeans, in other words the Indian imagination of us! Of course they were responding directly to experiences with European-Americans and not a series of pulp novels about them!
Here's an example:
All that being said, I would certainly LOVE to see accurate depictions of specific Indian cultures, and other cultures as well. I think such sets would be massively popular with audiences who know not of Playmobil.