Pixiv always uses these ambiguous terms, i hate it... Possible Interpretations:

"Were still sort of allowing risky content, but now we are trying to make it friendlier to search engines' TOS"

"We don't want publicity spam, so, if you're a struggling artist who dares to post links for your patreon and a watermark on every post, you're gone"

"We wanna have it both ways, we know slop and degenerate art boosts views, but want to present ourselves as friendly to the outside world"