Tyne and Wear metro: Tynemouth to Airport; only 2 zones?

Zones are an often unfair but nonetheless common way to organise public transport systems.
On the Tyne and Wear Metro I think I've noticed a bit of an oddity in this however.
If I was to start on the coast, say Tynemouth, then would a journey to the airport count as only 2 zones for me?
Gosforth is on the zone 1/2 border and it is technically possible to change trains there, which would give us 2 zones, however the more common route that people take is via Monument, which should be 3 zones.
Am I correct in this?
Under what rationale is it cheaper for someone to reach the airport from this distance rather than for instance the considerably closer Ilford Road?
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Full Route Journey: Green Line | Tyne \u0026 Wear Metro - Airport To South Hylton | Metrocar 4059
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