The DC travel guidance doesn't appear to have been updated since May 20, 2021:
From this page:
https://coronavirus.dc.gov/healthguidance you can link to
https://coronavirus.dc.gov/sites/default/files/dc/sites/coronavirus/page_content/attachments/Travel_Guidance_DCHealth_COVID-19_2021-5-17-2021.pdf
HOWEVER, amusingly, the OSSE guidelines pertaining to schools are different:
https://osse.dc.gov/sites/default/files/dc/sites/osse/page_content/attachments/FINAL_OSSE_Health_and_Safety%20Guidance_for_Schools-COVID-19_Recovery_Period.pdf?fbclid=IwAR1R8RPPJXN9MPWEIG1qO8rCcjbf4DbXcpgNgk16wDZYrcd77FE1GiYUKgs
School guidelines were updated June 25th, so are more up-to-date. However, they link to the May 20th guidelines.
The difference is for the unvaccinated and domestic travel:
In the May 20 document, the unvaccinated have to quarantine for 7 days after returning home from domestic travel outside of MD/DC/VA, regardless of a negative test 3-5 days after return. If they don't test, it is 10 days.
In the OSSE document, there is no direct mention of that 7-day quarantine, and only mentions testing after 3-5 days. If one doesn't test it is 10 days quarantine.