The tidal range at a particular location is the difference in height between high tide and low tide.
Conclusion
The magnitudes of tidal ranges must be explained entirely by gravitational forces.
Evidence
The only forces involved in inducing the tides are the sun's and moon's gravity.
Evaluate
Given that ... only gravitational forces (from the sun and moon) are involved in inducing tidal ranges,
How could we argue that ... there are non-gravitational forces that affect the magnitude of tidal ranges?
To induce something means to trigger it, to start it. In maternity wards around the world, doctors and nurses will induce labor with a drug if it's not happening on its own.
The magnitude of something is its scale. In this case, it's the difference between high tide and low tide.
Is it possible that only X is involved in starting something, but other factors besides X affect the scale of how that thing plays out?
Sure. The catalyst of something doesn't have to be the only thing determining its shape / scale. Maybe without the sun and moon, there'd be no such thing as a tidal range. But maybe other things affect how big that tidal range is (such as weather / strong winds / local underwater topography ... i.e. does the beach slowly ramp down to the ocean floor or reach a cliff's edge where it suddenly drops a ton).
If Max went around town shoving people down to the ground, we could say that he's the only force involved in inducing people falling to the ground, but is the magnitude of people's fall entirely determined by Max?
No, it might matter how heavy they are. Whether they're standing near a stairwell. Whether they're standing on soft ground vs. concrete.
Goal
Look for an answer addressing the fact that even though one thing (gravity) is responsible for starting some action/event, other factors could still contribute to the size of that action/event.