That has been the process for at least 10 years now. Not sure about before that. I wouldn't be surprised if there was a time when hand washing glasses in the bar sink was considered an acceptable practice for housekeeping. Acceptable standards have changed significantly over the years.
That's why the test is being conducted. SSR is the WDW resort most impacted due to its size and spread out nature. The current standard for glassware dictates it must be professionally washed and/or sanitized, which cannot be done inside the Studio room. Housekeepers must swap out all of the glasses and mugs between guests, transporting the removed glassware to central dishwashing stations for proper cleaning.
There are over 400 Studios at SSR, so I imagine the costs associated with that process are noteworthy.
Members who feel strongly one way or another are encouraged to voice their opinions to
DVC. The fact that it's only a test process which hasn't expanded to other resorts suggests the outcome is still undetermined.