Assuming you are talking about a topology as can be seen below:
simulate this circuit – Schematic created using CircuitLab
Then yes, there are valid concerns to at least consider doing this with (some) linear regulators (in some situations).
In the event that the input is forced low & especially if there is larger output capacitance than the local input capacitance, you end up in a case where the output voltage is higher than the input with a relatively high source of charge.
This is a valid concern in the automotive industry and you find regulators with such a diode on-die.
SHORTING THE REGULATOR INPUT
When using large capacitors at the output of these regulators, a
protection diode connected input to output may be required if the
input is shorted to ground. Without the protection diode, an input
short will cause the input to rapidly approach ground potential, while
the output remains near the initial VOUT because of the stored charge
in the large output capacitor.
The capacitor will then discharge through a large internal input to
output diode and parasitic transistors. If the energy released by the
capacitor is large enough, this diode, low current metal and the
regulator will be destroyed. The fast diode in Figure 21 will shunt
most of the capacitors discharge current around the regulator.
Generally no protection diode is required for values of output
capacitance ≤ 10 μF.