The issue here is that you’re not actually using virtual tables – you are using physical tables created via DAX expressions. Virtual tables exist only within the context of measures. It might sound like semantic hairsplitting, but the implications for size and potentially performance are significant.
If you want to reduce the file size, you will need to create truly virtual tables using variables within a measure. Here’s a recent example of extensive virtual table manipulation I did that used a similar stepwise approach to the solution that you used above for your DAX expression tables. (Note: the example is somewhat of a nonsense approach, since DAX was not the proper tool in this case but is a good illustration I think of the power of manipulating virtual tables through variables).
I hope this is helpful.
- Brian