my understanding is based off of this thread https://www.dndbeyond.com/forums/d-d-beyond-general/bugs-support/22164-warforged-fighter-defensive-fighting-style and the embedded tweet from mike mearls that very clearly show the intent does not currently match the RAW and that RAW in its current iteration has medium and heavy integrated counting towards unarmored bonuses.

I'm not arguing that its rules lawyery or advocating being annoying about it. but if knowledge of the system vs intent is not at least discussed then you're missing out on important information that might affect your playstyle. i specifically chose to not take defensive fighting style on my warforged fighter because i didn't want the RAW vs intent interpretation to affect my character in the opposite direction (relying on intent where a dm might rely on RAW) so i thought it was important to share that knowledge