XSD vs ISO seconds fraction separator

Hello all,

Regarding dateTime (and similar time types):

ISO 8601 specifies that seconds and fractions of seconds are to be 
separated by a comma or a dot, with comma being preferred. The XML 
Schema data type 'dateTime' allows only the dot. This difference is a 
bit of a nuisance when validating ISO conforming date-time values with 
second fractions. Is this deliberate, or could this be considered an errata?

Thank you.

Sincerely,
Daniel Vogelheim