Hi Megan,
how are you? My answer to all ADUs in Washington DC is "yes, but..." In Washington DC you have the right to develop a secondary unit in your property. Based on the zone (R, RF, RA, etc) this secondary unit has a particular name. Still, technically all buildings are (or have the potential to be) identical. The cost of construction, the impact on the existing building and site will be the main limits you have when deciding where and how to develop the secondary unit.
I am happy to schedule a call to guide you on the criteria you want to follow for your adu. We can talk about budget, scope and site... and yes, "fuzzy zoning" as well (but it's not that fuzzy, honestly).
Looking forward to hearing from you,
ile