Reproduction steps:
1. Open the attached project "Profiler Bug.zip";
2. Open the Test scene;
3. Enable the Profiler by clicking "Record";
4. Enter a Play mode;
5. Compare the values in the Console (from TestScript) to the Profiler values.

Expected results: Values shown in the Console, which are results of Recorder.elapsedNanoseconds method, should match with values given in the Profiler for all samples.
Actual results: Values do not match for render samples (such like Camera.Render).

Reproduced on: 5.6.3p4, 2017.1.2p2, 2017.2.0f3, 2017.3.0b6, 2018.1.0a1.

Profiling.Recorder API captures all events whenever they come from editor or playmode.
To capture something which is limited to a playmode Recorder must be enabled only for the game logic duration in the editor.
Also in 2018.2 Profiler Native Plugin API allows to make Recorder-like class with advanced custom functionality (e.g. per thread capture)