Who does THAT? That just sounds like a disaster.

What we're talking about is shaving a couple of millimeters off the actuator pin, or putting a washer under the bi-metal strip to raise it a couple millimeters. A 2mm reduction in the inserted depth of the actuator pin, either by raising the bi-metal strip or by shortening the pin itself, is good on the OEM sachs clutches for around a 10c reduction in engagement temp. The high-rpm cutoff still works as it should, as does the rest of the clutch.

The only thing you're changing is the engagement temp. Certainly nothing unsafe about it, and you're not "locking" the fan, it still engages and disengages as it should, just at a lower temperature. The factory setting is around 100c, so by the time the fan is fully engaged the car is already running hot. Lowering it helps your operating temps, as well as your a/c performance.