Are you saying Muslims are not actually trustworthy?
People cannot be friendly with each other just for the sake of being friendly?
A Muslim in lands of Kuffar is being friendly because that is evangelising and not to do that is a sin?
That is messed up if I have understood it correctly.
I'm certainly not saying Muslims are not trustworthy. Muslims are no different than any other group of human beings - they contain, good, bad and indifferent.
To generalise that Muslims are untrustworthy is to play straight into the hands of 'Taqiyya Tactician' mentality of many bigots these days who want to justify their bigotry, hatred, and even violence.
Without doubt Muslims frequently form very genuine relationships with non-Muslims without there being any hidden agenda to convert.
Having said that, many will be conscious of trying to show a 'good example' of Muslims and may even talk about Islam if the subject arises. But that is no more 'sinister' or "untrustworthy" than any other human being who shares their views, thoughts, beliefs, ideas etc... with friends.