See this news article: https://www.xda-developers.com/onepl...ating-reviews/
Long story short - all cores on a test device were bumped to max performance (and stayed there) whenever a benchmark app was run.
This was done by identifying the app name (package name). Very simple and crude implementation.
Graph of performance when running a custom build app with no identifiers:
Same when running standard apps with regular identifiers present (the phone is now cheating):
Dick move OnePlus! Still ordered the phone though