I understand what you're after. But what you're asking for creates a problem I'm not sure you're seeing. Look at the example screenshot I've attached, particularly the My Expression column, showing some made-up data that should illustrate the issue (using the first setup I posed).
At the Artist level, you're going to have:
The Beatles
and drilling down, you'll then have:
Abbey Road White Album
When you drill down into Abbey Road, no problem - MC takes you directly to the file list and you see your tracks (because there are no tracks now with any [Master] values, likewise [Disc #]).
But, when you drill into the White Album (going to the [Master] category), here you're presented with a problem. MC shows:
Remastered Unassigned
You're asking for this:
1 2 Remastered
which doesn't make sense as at this [Master] category level, 1 and 2 are not [Master] values, they're [Disc #] values.
Once MC has any value for a category, it can't collapse that category and must assign all unassigned values into the generic Unassigned category.
If you want to force the issue, setup the following under Details in your Theater View configuration:
Album Artist (auto)
Album expression
and set Album expression to be an expression category with the following:
ListBuild(1, \, [Album], [Master], [Disc #])&datatype=[list]
This will give you exactly what you're asking for.