So you are basically fine in that you still maintain 16 bit resolution and dynamic range.
But if you paid for and play 24 bit material and lose 8 bits (via the digital Volume Control) you're at 16 bits and "didn't get your money's worth" out of your 24 bit music purchase or stream.
You lose resolution and dynamic range but the question becomes, does it matter ? It is a moot question if you refrain from using the Digital Volume control and maintain all 24 bits and control the volume in the analog domain with a preamp.
Related but not about digital resolution as discussed above:
I have used Digital Volume controls on some DACs. Some are better than others but unrelated to the number D/A bits. It seems that many DACs on their own (IMHO) lack the robust, dynamic, and full bodied sound that can be achieved with a good outboard preamp. Some DACs will sound slightly less 'alive' or 'dynamic' and I attribute that to their analog output section and limited drive vs a good preamp.
