This is just plain not true. They very clearly ban AI-generated NSFW content, hence the removal of the subs:
>Additionally, images or video of another person posted for the specific purpose of faking explicit content or soliciting “lookalike” pornography (e.g. “deepfakes” or "bubble porn") is also against the Rule.
I Google'd "reddit rules", this[1] page was the top result, and under "Rule 3" the reader is linked to this[2] page, with the above quote.
[1]https://www.redditinc.com/policies/content-policy
[2]https://www.reddithelp.com/hc/en-us/articles/360043513411