I got it, silly typo.

{
  "id": 2,
  "srid": 4326,
  "coordinates": [
 --->[
       [-77.292894, 38.392816, 0], [-77.169498, 38.468925, 0], [-77.204214, 38.568971, 0]
     ]<---
  ]
}

Extra set of brackets so it was getting a List<List<List<Double>>> a mismatch to what the LineWithinRequestID's coordinateList was expecting