Oh, come on now, a husband can touch his wife's breasts or buttocks at any time without sin. There need not be a proximate intention to consummate the marriage act, as a certain amount of intimacy can entail a remote preparation for such activity.
If you are responding to my comments, I reaffirmed that this is not sinful, and was submitting that no priest I can imagine, would ever say this is sinful. Way,
way out on the fringes of the internet, you will find websites that make some pretty outlandish assertions --- that the BVM is God, that there has been no valid pope since Pius IX (yes, Pio Nono, as in
Syllabus of Errors Pius IX), that there has been no valid pope since around AD 1100, and so on. On sites like that, yes, you
might find an assertion such as the one you cite. But other than sites like that, I don't think so.
The closest thing I can imagine would be a couple who is practicing NFP but has a certain difficulty with abstinence and, as a result of engaging in such licit embraces, might be tempted to alleviate their concupiscence through masturbation or non-procreative acts. But that does not make the intimacies in themselves sinful. Another close analogy would be when couples are involuntarily separated for a time (e.g., military service, husband has to travel with his job, wife has to go stay with an infirm family member), and reflecting on each other's physical attributes, and intimacies they have shared, could cause them to fall into solitary vice.