The concept of "mutuals" is fundamentally influencer-centric. A person who uses their account for reading rather than just posting only hurts themself by refusing to follow an account that doesn't follow them back.

"See who your real friends are" is either:

1) confused branding that conflates two unrelated user domains

2) grossly and manipulatively trying to make people feel bad by pushing the idea that following means friendship and needs to be reciprocal