Why does the high reverse bias voltage in a PIN diode circuit not damage the op-amp?
It is blocked by the coupling capacitor CC, and even if CC failed shorted, the current is limited by RB1 to less than 300nA.
IC1A can withstand an input current through the protection diodes that is 100,000 times higher than that, according to the datasheet.

So the 300nA will be safely clamped to slightly over the power supply voltage. That's technically outside the stated absolute maximum rating for input voltage, but in fact completely safe.
However if someone were to carelessly short the PD during operation the discharge of CC through the op-amp input could damage it.