Anthony Pl S is a public ROW..  it connects to 27th Ave S, and happens to be platted on a diagonal relative to 27th Ave S, the alley, Cheasty Blvd.  but it is a straight line, and terminates exactly where OSM shows it terminating. It provides access to 3515 and 3517 Anthony Pl. S..  

3523 & 3529 Anthony Pl S. are accessed from the platted public alley (west of them), which connects to Cheasty Blvd.     

These two access roads do not connect to each other as currently shown on OSM.   King County IMAP is showing it correctly, so please refer to that resource.  Thank you! I appreciate your help. 
https://gismaps.kingcounty.gov/imap/