some centuries ago first voltage regulators were these L7805 or µA7805 (for 5V output) and for audio circuits you use larger capacitors on input and output to get a voltage with less noise.
In datasheets you find often a diode parallel to voltage regulator, so current can flow from output to input. The explanation - this one is from ST datasheet - tells:
Today you find a voltage regulator AP211K on sensor boards with BMP388 or BMP390 (Product ID: 3966 and 4816). You can power these boards with 5V, if you are using an Arduino board. Other MCUs are working with 3.3V and 5V will kill GPIOs.Application with high capacitance loads and an output voltage greater than 6 volts
need an external diode to protect the device against input short circuit. In this case the input
voltage falls rapidly while the output voltage decrease slowly. The capacitance
discharges by means of the base-emitter junction of the series pass transistor in
the regulator. If the energy is sufficiently high, the transistor may be destroyed.
The external diode by-passes the current from the IC to ground.
So what will happen, if you power sensor board on the 3.3V pin?
I see a "... you can use it with a 3V or 5V logic microcontroller without worry" in description. But is it really harmless for the regulator? In datasheet, I don't see a remark about this condition.
Bye
Jürgen