The “save ink/toner” feature of print in Acrobat DC is actually an integration of the Adobe LeanPrint product into Acrobat's print pipeline. Simply stated, it uses ICC color management with special profiles designed to minimize ink usage. Nothing more, nothing less.
Since it isn't optimized for any particular print technology, inks, or technologies, YMMV (your mileage may vary) in terms of (1) any resultant ink savings and (2) the quality of the output. It should be noted that most modern printers, especially consumer and office devices, have built-in “economy modes” that you can usually access from the printers' setup properties; these device specific features are generally much more effective.
- Dov