An example of a “low-quality” submission would be a user attempting to name-squat a well-known brand name or project name without any clear affiliation with that organization. The process involves verifying whether there is an affiliation or not, and whether that person should be the owner of that organization.
Because GitHub and npm are owned by a large, multi-billion dollar corporation and can provide paid support staff for those services to deal with spam and namesquatting events retroactively, whereas PyPI is owned by a non-profit foundation, maintained by volunteers and currently has a paid staff of effectively 1 person, although it has a comparable volume of users.