What is the point of setting an upper limit in Auto-ISO?

Then you are saying that regardless of the metering selected, Auto-ISO does not clip highlights. I do not believe that,

You are making things up. Post a link to where you claim I said that.

You asked

and I replied

You said that

I read your claim that this is regardless of the selected metering.
If 90D had one metering (a special do-no-clip-highlights-in-Auto-ISO, or a strong highlight-weighted one) then I could believe it ... kind of.

Then you made an incorrect assumption by assuming I have used all the metering modes. I didn’t mention metering modes at all so if you were in doubt you should have asked instead of assume.

One might set an upper limit on ISO to alert themselves to some other semi-auto guardrail that they have in place and forgot to remove. Like shooting aperture priority with a high minimum shutter speed for a sporting event yesterday. Then today you’re taking indoor pictures and you’re at ISO 20,000 and 1/1,000. Maybe bumping up against the ISO cap gives you a blinking setting reminding you to remove the minimum shutter speed.

Which metering mode did you use that does not cause any highlight clipping in Auto-ISO?

It might be silly approach, but it worked for me, kind of...

I set the upper limit of ISO speed to not get noisy images. With given exposure and given maximum aperture and ISO speed I didn´t get the brightness, the camera reminded me with blinking, that the image is unobtainable by my standards. I either had to add risky shutter speed, or add light, or wait for light, but at the momentary circumstances, things went red and I knew I could spare my battery and efforts.

It was not the wisest tactics, because now I might miss some photos, which I could delete if I didn´t like them, but oh well, no failed shutters and no biggie. :-)

"What is the point of setting an upper limit in Auto-ISO?"
In my tests, I found that it prevented the ISO from automatically going higher than I specified.

Yes, indeed it prevents ISO from rising above the set limit. The question is why would you do that.
In A mode it forces shutter speed below the minimum shutter speed that you set.
In M Mode it darkens the EVF.
Others have posted why they still prefer to set an upper limit.

You are again making things up.

I never said Auto iso does not cause highlight clipping. I said on my 90D I have never seen highlights clipped due to Auto ISO when the camera set ISO above base.

I normally use evaluative/matrix metering.

In my experience the 90D is over cautious when setting ISO above base with Auto iso to protect highlights after I set the exposure*.

Are you saying that 90D meters differently with Auto-ISO on and off? I have not noticed that on my R5 or other cameras. In my experience, the only way to force metering to protect the highlights somewhat was to use highlight-weighted metering, and even that does not always work.

I just posted my experience with my 90D.

The Auto iso is over cautious when setting iso above base when using evaluative/matrix metering.

So with the camera in manual mode and automatic ISO giving you iso 100, if you stop down one stop, are you saying the ISO doesn’t go to 200?

No, of course not.

But as I posted earlier, I set the optimal exposure** first and then let Auto ISO set iso where it likes as long as highlights are not clipped.

I would have no reason to stop down because the exposure* would no longer be optimal**.

Exactly. It’s simply an option for trade offs. Sure you’ve set the min desired shutter speed. But setting an auto ISO limit expresses that you’re willing to “give” on shutter (over your ideal minimum) if ISO gets too high for you. That said, I never use auto ISO.

So the ISO behavior with light level is linear? Then how is " Auto iso is over cautious when setting iso above base"?

Your last sentence above is not relevant to the issue " The Auto iso is over cautious when setting iso above base when using evaluative/matrix metering."

The op asked what is the point in setting an upper limit for ISO in Auto ISO.

I simply posted why I set Max iso to the highest native ISO value.