We were running into issues where the documents grew too large for being passed as a string to emacs, and we need to handle #+setupfile so we need to start handling org-mode documents as files and not just as anonymous streams of text.
The anonymous stream of text handling will remain because the automated tests use it.
This is not meant to produce publishable or comparable benchmarks. Such a script would have to run many iterations with the input already loaded into memory, proper prioritization via nice/ionice, and have a warm-up phase. This is just automating a basic test I am frequently running to compare parse times when investigating performance issues.