Voltage supervisory circuit selection
I've seen cases where people undervoltage (or overclock for a given voltage) to get more performance per power. So manufacturers tend to have a safety margin on wether an IC should work or not at a given voltage. I would not expect a detailed statistical report of functioning outside of the recommended values though. Even if you are be able to achieve operation on a given batch at lower voltage, that does not guarantee future operation of other batches of ICs.
Even though an MCU (as you mentioned) might state 1.7V minimum working voltage, it will probably not have all the performance it has at "ideal" voltage (say 3.3V or 5V). It might need to work with a lower frequency, for example. I'd expect the detection circuits to work from the threshold (1.1V on your example) all the way to 0V.


You can then either set a brownout threshold to turn off the MCU (most have this feature buit in) or as you mentioned build an external supervisor circuit.