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 :::Now that you have done some digging, you realize why your edit had to be reverted. The secret designation is necessary for MDSHA to inventory the NPS portion of the parkway, particularly because there is a seamless transition between the NPS and MDSHA portions of the parkway. There is also a seamless transition between the MDSHA segment and Russell Street, which is maintained by Baltimore DOT. Keeping inventories of roads maintained by other agencies is not strictly necessary, but it is very helpful. Contrast with the Kansas Department of Transportation, which pretends the Kansas Turnpike does not exist. 

 :::As for why MD 295 and DC 295 do not connect, it helps to know the history of the area. The Baltimore–Washington Parkway and the portion of New York Avenue west to Bladensburg Road were completed in 1953 or 1954. There was a seamless transition between New York Avenue and the parkway, which explains why the MD 295 inventory begins at US 50 near the Anacostia River. The current course of MD 201 was built between 1953 and 1957; the Kenilworth Avenue expressway that carries the DC 295 designation was completed in 1957. If you look at the Maryland Route 201 article, it is MD 201 that links with DC 295, not MD 295. US 50 east of the southern end of the parkway, John Hanson Highway, was completed in 1962. The three routes were constructed close enough together in time that it is almost certain they were planned to converge in their current form. The inventory is likely a reflection of that order of events. '''''' "