GIPS Input requirement versus recommendation

Standard 1.A.4 states that starting 1/1/2010, firms MUST value portfolios as of calendar month-end or last business day of the month. However, one of the recommendations (Standard 1.B.3) states, calendar month-end valuation or valuation on the last business day is recommended. So, what is the point of requiring then only to include as part of recommendation? Any thoughts?

Is this the 2010 version of GIPS? This would make sense if it were the previous version.

This means that before 1/1/2010, its not required yet, but recommended. After 1/1/2010, its required.