Breakfast, where is your source for the 28 days that you mentioned??
You will not find any definitive UKBA answer on this specific.
This is what is currently stated in the latest version of the Immigration Instructions for spouses:-
There is no specific requirement in the Rules that the entire probationary period must be spent in the United Kingdom. For example, where an applicant has spent a limited period outside of the United Kingdom in connection with his employment, this should not count against him. However, if he has spent the majority of the period overseas, there may be reason to doubt that all the requirements of the Rules have been met. Each case must be judged on its merits, taking into account reasons for travel, length of absences and whether the applicant and sponsor travelled and lived together during the time spent outside the United Kingdom. These factors will need to be considered against the requirements of the Rules.
No mention of any 28 day restriction.
No mention of any absence restrictions other than 'majority of period'
Even work permit or points based system people making ILR applications are not restricted to such short absences as 28 days per year.
