(a) Until December 31, 1987, this chapter shall apply only to residential developments.
(b) On and after January 1, 1988, an ordinance adopted pursuant to subdivision (g) of Section 66452.6 may differentiate between residential and nonresidential developments in prescribing the initial time period after which the rights conferred by a vesting tentative map shall expire. In no event, however, shall that period be less for residential developments than for nonresidential developments.