Multiple measure rests, implementation notes clarification

[dbuenzli]

In the implementation notes of rests it is written:

Scoring applications should draw multiple measure rests using primitives to provide variable width and line thickness rather than using restHBar.

In the engraving defaults I can only find hBarThickness, but not values for the starting and end marks. Am I supposed to use restHBarLeft and restHBarRight for these ? If that's the case maybe the note could be clarified.