This may be a script or visual issue, as I'm not seeing this mission having a personnel requirement at all.
I've also checked with a clean (non-script version), no mention of personnel.
I'll run some tests and see if I can reproduce this issue.
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UPDATE: Sent an HRV+Boat to a call and it fulfilled the Heavy Rescue requirement but not the Firetruck requirement (expected behaviour).
However, it did not appear to advise that personnel were missing.
We have a second mission testing in progress, will advise on results.
UPDATE 2:
The second test same results, this time the HRV+Boat only had 4 peoples on it.
On that call, we then sent a vehicle with only 1 FF on it and it went green.
Unfortunately, I am unable to reproduce this, it seems to be either a visual bug or a local script issue.