There appears to be some nuanced interpretation of when the participant notice is required.
Backing up a little bit, the IRS was concerned about 2 issues going into Cycle 3 about the match needing to be definitely determinable. The first issue was the total amount of the match to be funded had to be communicated by the employer to the Plan Administrator or Trustee before the contribution was deposited into the trust. This is a simple formality and parallels the documentation required for specifying a discretionary profit sharing contribution.
The second issue was whether the match is definitely determinable meaning do participants know who gets the match, what is the frequency the match is made, and how is each participant's match calculated. The elements needed to determine the match include specifying:
matching period (e.g., annual, each payroll, quarterly...)
allocation formula (e.g., fixed percent, percent by tiers, flat dollar...)
eligibility (e.g., varying allocations by business unit)
If all of these elements are explicitly defined in the document (some plan say "fixed", "rigid" or similar adjectives implying could only be changed by plan amendment), then there is no need to send a notice to participants. In this instance then the SPD effectively communicates to participants about a definitely determinable match in the same manner in which a discretionary profit sharing contribution is communicated to participants.
If any of these elements are not explicitly defined in the document (the plan sponsor can has discretion), then a notice is required to be sent to participants within 60 days after the last match is funded for the plan year. This timing requirement could vary considerably from year to year.
One interesting note is the notice is an IRS notice (subject to the IRS rules for electronic delivery), why the SPD generally is a DOL disclosure.
Another interesting note is that the notice requirement seems to apply to only to pre-approved documents. Apparently an individually designed plan possibly may not be subject to the notice requirement.