Comparision of bedroom antics in relationships vs brief encounters?

Im asking this question because i was watching sextips for couples last summer and a couple of lady's said (well they were lady's before they went on that show)lol,that they can be dirtier in bed with a brief encounter than with there boyfriend's and i wanted to know whether this applies to most girls.I feel it should be the other way round and things like A**L sex etc are more acceptable in a relationship and then can be seen as a measure of the womens feelings for her man,the more comfortable she is with him the more adventurous she'll be with him.