Power supply of STM32F415RGT6

I have been trying to understand the power supply scheme of STM32F415RGT6 but I found it looks confused to me.
The page claims:

at the same time, STM4’s spec claims:

So, my first question is what is the main idea of “to cause the internal regulator to disable itself”? According to the STM spec, the internal regulator can only be disabled by the BYPASS_REG pin which is not available on our TQFP-64 package. And it sounds we cannot disable the internal regulator by applying higher voltage on the VCAP1/2 pins. …Maybe I am not aware of this way to disable an internal regulator.

And the second question is why VDD pins are not considered to measure power supply but using the VCAP1/2 pins instead?

Linear regulators work by turning on and off based on its output voltage exceeding a certain value (~1.2V in this case). If you feed in a higher voltage than the regulator wants to output, it never turns on.

You don’t want to measure on the high side of the regulator because a) the switching of the regulator will disrupt your power measurements and b) output capacitors that are usually required for a stable output voltage will filter out the information that you’re trying to measure.

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I guess it is like analogy when water with higher pressure stops water with lower pressure.

Looks like 1.3V should be fine. Will 1.4V damage the microcontroller?
BTW, the VCAP1/2 voltage is 1.25V.

Yup, 1.3V should be good. I’m not sure at what point you’ll start to risk damaging the microcontroller.