Yeah, there's a disconnect somewhere:
1. In the main/subgroup settings screen, It implies the same rules apply for either naming a main or a subgroup, the blurb displays the same: "no spaces, pluses, slashes, or underscores"; no period is mentioned.
2. The code will not let you use a period while naming a main group, and the Owner manual also states periods not allowed.
3. The code will let you use a period while naming a subgroup, but the Owner manual states periods not allowed.