That's the thing. For some people oral(giver) can be the most pleasurable, so for them oral sex would just be "sex" as for other vaginal is, and vaginal for them can be viewed not as sex at all, but just a reproductive activity. For such people replacing oral sex with anal sex would be Anal Only. Human sexuality is so complex that there is not even enough English words to explain anyone's sexuality shortly.One sided as in it doesn't bring pleasure to one side
And by it being not quite same type I meant it often may not be seen as the "main course" the way vaginal and anal would be
I'd like to add that "only" is quite a relaxed word, not having any other sex/sexual activity other than anal would rather be called anal exclusive.Heck, the fact that "Anal-Only" strangely allows for oral, never sat right with me. I'd personally call this kink "Pussy Denial", that'd be more accurate.
Just google the difference between only and exclusive. I found an example i that i think should clarify a lot.
One common mistake people make is using “only” when they should use “exclusively.” For example, saying “I only eat pizza” implies that pizza is the only thing you eat, but it doesn’t necessarily mean that you eat pizza exclusively. On the other hand, saying “I exclusively eat pizza” means that pizza is the only thing you eat.