I think I'm understanding what you are saying
and for your question, yes I cover my head when we have non-mehram guests at home even if I dont wear hijaab on daily basic. I dont think I do it from an Islamic POV, but rather it is a cultural thing .. Maybe something with respect? .. Well really I've never thought about it .. Its something that comes naturally to me when we have male guests at home that we cover over the head with the dupatta .. Actually I do it infront of my grandpa.. as well as some elder uncles and some uncles of my mum .. so nothing to do with na-mehram issue ..