It is confusing, but I think Section 18 has to do with the timing for document providers to submit the next generation of documents for approval.
Section 16 addresses the timing for employers to adopt the approved plans.
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.03 When the review of a cycle for pre-approved plans has neared completion (after approximately a two-year review process), the Service will publish an announcement providing the date by which adopting employers must adopt the newly approved plans. This will be a uniform date that will apply to all adopting employers. Depending upon the length of the review process, it is expected that this date will give virtually all employers approximately a two-year window to adopt their updated plans. For purposes of this revenue procedure, an adopting employer means an employer who satisfies the requirements described under section 17 of this revenue procedure.
.04 An adopting employer that adopts the approved M&P or VS plan by the announced deadline will have adopted the plan within the employer's six-year remedial amendment cycle. The announced deadline will be the end of the plan's remedial amendment cycle with respect to all disqualifying provisions for which the remedial amendment period would otherwise end during the cycle.
The deadline was published in Announcement 2008-23.
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Deadline for Employer Adoption of EGTRRA-approved Defined Contribution M&P and VS Plans
An adopting employer whose plan is eligible for the six-year remedial amendment cycle under section 17 of Rev. Proc. 2007-44 and that adopts an EGTRRA-approved M&P or VS defined contribution plan by April 30, 2010, will have adopted the plan within the employer's six-year remedial amendment cycle. 1 The end of the plan's remedial amendment cycle with respect to EGTRRA and the changes in plan qualification requirements on the 2004 Cumulative List is April 30, 2010.