Maybe its the introducer DHV for YOU
as they obviously think YOU are worth the person talking to, or maybe they would rather you talked to this person so they can go off elsewhere? 
Think if you were the one doing the introducing, about why you should intro a girl to a guy.
You will have to decide as you politely accept the intro... bail or game.
Either way you have skipped the opener? straight into Kino - hand shake or isolate if the person could be worth gaming?
If its a SHE doing the intro then you could consider it to be DHV, if its a HE then maybe its also a DHV unless hes AMOGin you by using a flakey girl... ? depends on the person and their motives at the time of introduction..
Have you had a similar experience and how did it go, who was the person introducing? what was their status and motives? unless its the bosses daughter
.. maybe use this question as an opener to ask about "politeness v attraction in a casual intro situation" to the next one you are intro`d to or out in the field. Get a female perspective ? there are some on this forum go ask them...
J1f