Well, from here on I guess it's speculation. I suppose they could have been taken off a Pochahontas set, but that almost raises more questions than it answers (like, why?).
The recurring tinplate question: what was going on in the toy factory in 1929? We'll never know, but there are many known cases of parts bins being raided to complete sets with parts from something else - especially towards the end of production runs. Just my opinion, but there's as good a case of this coming from the factory like this, as there is of it being replaced later.
Nice set by the way, looking good!