The best guess is some of both. If they're tall girls there's a reasonable chance they're attracted, 'cos they have trouble finding guys who aren't shorter than them (this is NOT personal experience)., and it feels a bit awkward to be taller than your bf.
I 'won't lie I think I get away with more (looks wise) because of my height. I'm not quite 6'10 ( I'm 6'1) so in your case it probably is both. Either way it is a good thing . It gives you an opening and you must take it