Because it assumes a uniform working year. Term-time-only contracts, variable timetables and cover arrangements all become exceptions typed in by hand.
Certifications and clearances are tracked on a spreadsheet, and the renewal that lapsed is found during an inspection.
Working patterns handle term-time and part-year contracts as patterns rather than exceptions, so leave accrual and pay are right without manual adjustment.
Clearances and certifications sit on the personnel record with expiry dates and the documents attached.
It will not build a teaching timetable. It holds availability, patterns and qualifications; timetabling is a different discipline.
It also does not verify a clearance with an issuing body.
Cover is arranged against who is actually available and qualified, and the cost of it is visible rather than absorbed.
Compliance reporting reads the record: who held what clearance on which date, with the evidence attached.
Yes, as working patterns, with correct accrual.
Yes, against the department it covered.
Yes, with expiry and acknowledgement.
Half an hour on your own numbers is usually enough to say whether Nest is the right place to start.