Of course it is! He is strong enought to carry her and she helps him wrapping her legs around his body! It's incredible the phsicologic effect that "wrapped legs around guy's bodies" produces me. When I watch a couple fucking in that way, I usually think "she has to feel a great pleasure because her wrapped legs around his boby is a clear signal that she doesn't wish he come out".
Unfortunately for me, I never had a girlfriend who wrap her legs around my body by her own because all my girlfriends prefered keep them spread all the time.
Yes, one time I had sex in a similar position like that. I was with my afro boyfriend making it over a chair sat over him face to face. We were outdoors my single house, so we fucked watching if anyvody could see us.
When we were close to clim our orgasms, my afro guy lifted me and he stayed standing carrying me until we cummed. I don't know how could he do that, because I was heavy for him...and he was shorter than me. Perhaps the extreme excitation gave him more strength...