SP playmates may indicate a trend toward SPs not wanting to settle down early, and to play around, I'm not sure that all SPs want to do are screw someone, but SPs may place a lot of importance on sexual compatibility, and may, for example, appreciate having an SJ helpmate partner who grounds them in practical ways...as long as they also are physically compatible and can do activities together. That's what I thought about it, is beyond sex, SPs probably place emphasis on "let's share hobbies/interests/activities" like keeping the relationship going not just through practicalities but through shared ...play. Through sharing their love of sports or film or music or travel, etc.
NF soulmates are self-explanatory, I guess, and the NT mindmate would be someone they could have intellectually stimulating convos with.
I personally do not believe in soul mates, but I do believe in sole mates; that is people being both compatible enough and mature enough to make a relationship work long-term.
Soul mates, to my mind, is a silly concept, and it's based in Jewish mythology, and if I get proven wrong someday so be it, but I'm not holding my breath. I think people just may think someone is their soul mate if they feel they are a good match for the long term.