Like it or not, that happens to be the way the Regulation was written in 1906. Not unlike many other archaic Regulations, to
not enforce it would be discriminatory. (Seen here:
http://www.uscis.gov/ilink/docView/SLB/HTML/SLB/0-0-0-1/0-0-0-45077/0-0-0-49904.html ... especially Section (b)(2)(ii)) Does it need changed? Well, it was in 1967... but it's so tightly knit with the military draft act, depending on very similar descriptives, that to change one has consequences for the other.
But, the lady in question could simply join one of the myriad secular organizations that are registered under the US Internal Revenue Service Section 503(c)(2) and easily meet the requirements of the Code.
Or, does the U.K. not have
any non-material, non-pertinent laws or regulations that haven't been modernized for decades if not centuries?
Seems to me to be a big hoopla about a gnat's rear end...