we have been instructed in at least 3 different parishes over the last 15 years or so to do exactly as OP describes, cross ourselves during this penitential rite. we have heard people scolded from the pulpit for striking the breast during the Confiteor or the Lord I am not worty.
However it does not bother me because I have received so much contradictory instruction from the pulpit over the years, we now just go with the flow whichever parish we end up. It reminds me of that old girl scout song, when you’re up you’re up and when you’re down you’re down etc. Hold hands, don’t hold hands raise them in the air, don’t raise them in the air hold them at chest level facing out, no facing in. Whatever.
Kneel. Stand, Sit, genuflect, don’t genuflect. What. Ever.
the laity don’t make this stuff up. any time you see someone in the pews doing something weird, unless they are mentally challenged, you can bet some priest, some time, somewhere, instructed them to do it.