The On-demand comparison filter has no pre-selected metadata types. So applying it has the same effect as the None (0) filter.
Our On-demand comparison filter is created for when you need to load up a comparison quickly when you click on Compare now on the comparison screen.
Once the comparison page loads, you can then add the metadata types you want to retrieve to your filter, or you can select your preferred filter (whether it's a custom filter you created or one of our pre-defined ones).
More details about using the new comparison window can be found here.
Metadata type–specific filter settings
Custom Object
When Custom Object is selected in the filter editor of an on-demand comparison you’ll see an option to automatically include related Profile and Permission Set metadata.