I think you will only see the actual masks when bringing the files into an app that supports cryptotomatte. For example, I use After Effects. Once I apply the Cryptomatte plugin, the various ways of accessing the mates become available. In After Effects, you have to click on a color that represents whatever object or material you set the mattes to in order to isolate that particular object or material. Once that is done in the manifest you can begin to use the selection as a mask.
However, it appears the Cryptomattes are only working with Octane output. Your file does not have Octane output selected. And if the default blender output is used I am not seeing any proper mattes being generated.
Could the devs step in to confirm that Cryptomattes only work with Octane output?