Because the version of CPDF we include with Dompdf has been developed the project that function was not necessary (Dompdf handles text wrapping). I'd have to review the commit history to see why it was removed, but likely the lack of intelligent text handling in that method led us to remove it (rather than build it out).
If you're building your PDF manually you might want to use the latest iteration of the original CPDF project (
https://github.com/rospdf/pdf-php). The
method that version uses is fairly simple, it just splits on line breaks then shifts the y position by the height of the text. Something that can just as easily be done in your own code.