It depends on the individual.
I often hung out 1 on 1 with my close female friend some time back even though she had a bf. Of course, I had no intent to do anything because only an ass break others' relationships (yes, i ended up falling for her but still kept it to myself until now).
But beware, no guys can be truly close to a girl without developing feelings.
Opinion on partner going out with oppo sex, Partner went out with opposite sex alone