I rest my case.
Not that I donno all these but I find that you are tying to prove something. I do not like to argue and I do not tend to over explain things if one did not ask.

 

And the current will be at it's max which is limited by the PSU's internal resistance

We need to distinguish between ideal sources and real sources. I did not want to confuse the student with this.

An ideal source and ideal conductors such that R=0 are not to be had in the real world. A real source has internal resistance, and a real conductor has a finite resistance.

When a real short occurs across a voltage source, there is a small resistance due to the resistance of the shorting wire and the resistance due to the supply's internal resistance. Hence a short does not really cause an infinite current.

Remember I = V / R

And so the voltage does not really go to zero.

V = I * R.

The real source does not actually have an infinite current available. Nor is the short really zero ohms.

Think about a battery. It has an energy equivalent to its stored electrical charge. When you short it the battery tries to deliver infinite current, but is limited by its physics, and the voltage across the battery tries to go to zero, but is limited by real physics. Nevertheless the battery obeys Ohms Law but with the inclusion of the battery's internal resistance and the shorting wire's real resistance.

If you put a voltmeter between the battery's terminals and watched the voltage, it would, indeed go to zero, but not instantaneously. And the current would try to be infinite, but is actually limited by the battery's internal resistance. Within a short time, the voltage would be zero as the charge within the battery was depleted. But, again, in the real world, something else would probably have burned up before the voltage went to zero.

In the case of a battery, a lead would melt and become open; in the case of a regulated voltage supply, a semiconductor would have been ruined and opened the circuit. And so on.