I agree with this ! However, here we are in a specific case and you have the correct final visual version for the format you are using.
As you choose
output: github_document, the final version is a Markdown document not a HTML document, so the final visual version is with markdown syntax.
There is a preview offered that opens in the IDE "asif" it was renderered on github. It won't be exactly the same as when previewed on Github (because Github has its own markdown renderer that will convert a
.md file using GFM syntax to a HTML view.
If you want to have the html preview locally, you can set
keep_html = TRUE for this format. That way the html file generated for preview won't be in a temp folder (default behavior) but save in the working directory.
If you use another output format (html_document, docx_document, pdf_document, ...), you'll have a final version that is the final format output.
Your question here is highly related to the use of
github_document format, which is a variant of
md_document which use GFM syntax. It is Markdown as input, and as output but not with the same markdown flavor.
Hope it helps understand.