That's pretty standard model for those times - when dealing with "inferior" peoples, its pretty much either "noble savage" or "inscrutable deceitful liar". The latter is especially convenient - if the observer does not understand something, it's not because their command of the local language and customs sucks and you can't actually understand a complex culture by just showing up there with zero knowledge - it's because the locals are taking pleasure in deceiving people.
Of course every culture has lying, some social customs necessitate it to some measure, and politeness, strictly speaking, always has a deceitful component - I am usually not really that invested in knowing how are you, and don't care that much about you having the best of luck in all your future endeavors - I am just saying that because that's a polite way to express that I don't hate you and neither you should hate me. And I may not actually be extremely busy this weekend but that's a polite way to say I don't want to go to the pokemon museum with you.
In a familiar culture, that's understood as how things work and is not taken at face value, but in context. Unfamiliar politeness could be taken by hostile (or arrogant) observer as deceit. Which is of course reinforced by being an outsider to the culture - would you really immediately tell everything about yourself and your intimate thoughts to a total stranger that looks weird and barely speaks your language? Or would you mutter some polite non-committal platitudes while he is scribbling away something like "never allowing oneself to appear as one is, but in always showing oneself otherwise; it is the art of presenting to each person the aspect that will please him most, of adopting his ideas, his tastes, his language, while inwardly remaining quite different". Fuck yes, I don't know you, and you are a guest, of course I'd not immediately go into dissecting the fine details on my soul and vigorously debating hot topics of the day with you.