As I wrote in the article, I already accounted for this. The raw combined performance degradation was 4x. APFS itself seems to be around 20%. Now that is somewhat rough, as APFS degradation may itself by non-linear. However, others have measured the pure APFS costs and they seem to be roughly what I saw:
https://www.macobserver.com/analysis/apfs-performance-lags-h...