What is better established is that BDSM practices exist within a developed culture of negotiating boundaries, risk, consent and participants’ needs. For example, research involving 202 BDSM practitioners found fairly strong norms around consent communication, although the depth of those negotiations varied depending on whether people were established partners or more recently acquainted.
Aftercare can reasonably be understood as a continuation of that communication: the discussion is not only about what happens inside the scene, but also what someone may need after it. That can matter particularly after experiences involving high physical or emotional intensity.
There is no need to invent a universal biology for this. We already know that people recover differently after intense experiences in general. One person wants to talk after a hard workout, another wants silence; sexual experiences can show the same individuality.
That is what makes aftercare interesting to me — not as a mandatory BDSM protocol, but as a good example of sexual attentiveness: we do not stop caring about our partner’s state the second the sexual practice itself ends.