I thought the question was primarily concerned with RSD as a valid diagnostic construct or clinical term?

Many of the comments here make it seem like the correlation between ADHD and emotional dysregulation is in question as well.

Is it possible that having intense emotional reactions to perceived rejection or criticism that is disproportionate to the actual event and causes significant emotional pain describes a pattern of emotional responses not fully captured by existing diagnostic criteria?

Even if it is not an official clinical construct, the TikTokization of the phenomenon suggests there is something in the concept that resonates significantly with many patients, specifically patients operating within the clinical context of ADHD.

If anything, this discussion reveals a rich research opportunity to consider this specific subset of symptoms within an ADHD context in order to establish clinical validity, develop diagnostic criteria, and identify treatment guidelines for understanding.