For here * sexual pleasure is sought outside of “the sexual relationship which is demanded by the moral order and in which the total meaning of mutual self-giving and human procreation in the context of true love is achieved.”*
Again, the point the Catechism seems to be making is that sexual acts which have life giving potential that are purposefully obstructed from actualizing that potential are wrong. This falls into the clear teachings of the Magisterium: masturbation, (completed) oral sex, sodomy, contraception, etc are wrong - wrong because they actively prevent life from being produced when there is natural potential for life in the acts. However, there is no life giving potential in the acts of “foreplay only” and is thus not part of the clear teaching the Catechism is alluding to here.
We can see this more clearly when you look at the case of NFP: clearly, sex during the infertile times of a woman’s cycle are not procreative - and yet they are not condemned as against or opposed to “the total meaning of mutual self-giving and human procreation in the context of true love.” Why not? Because there is no stifling of the potential to give life in the actions - it is open to the actualization of any life potential coming from those actions. The potential for life that is there is not obstructed from being actualized. Similarly, “foreplay only” does not obstruct any potential for life, as it has no potential for life. It is thus equally open to life as using NFP, since it does not obstruct the actualization of potentially procreative actions and is open to any procreation, were it to arise.
To me, much more clear Church teaching needs to surface for this to count as definite prohibition by the Church. Clearly some things are being condemned, but it seems like people are loosely lumping clearly distinct sets of actions in with already prohibited ones in order to satisfy their presuppositions about what the Church teaches. One important thing to ask is if any reliable and authoritative clergy member has taught that “foreplay only” is wrong. If not, then a massive burden of proof rests on those that condemn “foreplay only” as wrong.