I stumbled across this thread recently as i was having a similar problem trying to apply some logic to the "relevant" field of a "begin group" type where i had some required fields within the group. For me, i didn't need the fields to be required on my form, they were just set up to be required in the original feature service.
Anyway, in case this helps someone else, the way i achieved only having the "relevant" logic on the "begin group" was to put dummy fields inside the group (putting in "null" in the "bind::esri:fieldType" column for these fields since they weren't in my feature service) and then have my original, required fields outside this group with values in their respective "calculation" columns that referred back to the dummy fields.
So for example, inside the group you might have a field called HomeOwnerName_Initial. Then, outside the group, you would have a field called HomeOwnerName where in the "calculation" column it could say something like this: if(string-length(${HomeOwnerName_Initial})>0,${HomeOwnerName_Initial}, 'N/A'). Again, for me, i was just trying to deal with a situation where my original feature service fields required, but they didn't necessarily need to be required in the form itself.
