No, pdfHTML does all the work parsing the HTML and CSS, and mapping them to iText objects and styles. Then the iText engine renders the PDF based on these objects and styles.

However, pdfHTML doesn't support SVG for now, nor does it evaluate JavaScript. Support for SVG is on the development roadmap, and you could solve the JavaScript problem by using a browser engine to preprocess the HTML+CSS+JS. Examples of such a browser engine are WebKit (Chrome, Safari) and Gecko (Firefox). These can interpret the JavaScript and give you HTML that can be rendered by pdfHTML.

NOTE: SVG support was added to pdfHTML 2.1.0 in September 2018, and has been updated and improved in subsequent versions.