Images are still too big -- how to compress further?

Can you please elaborate if this is working as expected?

From: Image upload max size and further resizing regression issue

We don’t have a maximum allowed upload size site setting though. It’s only limited via NGINX.

And we also have another site setting to help downsize images: max image megapixels.

We try downsizing 3 times prior to creating the upload.

So there are two settings

max image size kb
and
max image megapixels

For example I would like to allow upload of photos up to 10MB and downsize them during the upload to 5 megapixels, So I’ve set:

max image size kb = 10000
max image megapixels = 5

Unfortunately if I try to upload 9MB file it shows

“Sorry, the image you are trying to upload is too large (maximum dimension is 5-megapixels), please resize it and try again.”

Is there any setting to really engage that 3x downsizing…? Because it just seems like both settings are just limits that test the uploaded file before it is processed.