I mean there's literally plenty of evidence which points right to it without them specifically mentioning death grip but apparently you need it spelled out for you by some impressive headline like "Science confirms death grip" because you can't put the jigsaw pieces together yourself.
Even look at how delayed ejaculation is often treated and you'll see right there.
Encourage a man who continues to masturbate to alter style (“switch hands”) and to approximate the stimulation likely to be experienced with his partner.
Do you think that switching to the left hand rather than the right just makes him a bit hornier or do you think it might have something to do with how tight he's gripping? 😂🤔
https://pubmed.ncbi.nlm.nih.gov/27652228/
And the following website run by the University of California says
While it is only estimated that delayed ejaculation symptoms are reported at low rates in literature (rarely exceeding 3%), clinical experiences, some urologists, and sex therapists are reporting an increasing incidence of RE and prevalence of self-diagnosed DGS.1 While the potential causes of RE vary widely and may be attributed to alcoholism and drug use, SSRI’s, birth defects, pelvic injuries, and nerve damage caused by diabetes, a five year retrospective chart review of men with delayed ejaculation indicated that 37 percent of patients had a history of masturbating in a way that stimulated a “specific spot,” or “with an idiosyncratic masturbatory style.”3 Continuously using too tight of a grip as with DGS or relying on extremely rapid stimulation characterizes two types of these styles.
https://sexinfoonline.com/masturbation-death-grip-syndrome-dgs/
If clinicians all waited for the supporting evidence before taking note of the phenomenon they are witnessing in their daily practice and providing advice for it then that would be harming many people, but luckily some sex therapists, psychotherapists etc do recognise it and don't just pretend it's some out-there theory....seeing as it actually makes sense.
There's concerned young men out there who have noticed that their masturbation habits have changed and how difficult it is to ejaculate now and they think it's due to how they masturbate (based on their own lived experience) and people like you want to say to them no no that's extremely unlikely, it's far more likely to be psychological or physical 🙄
There would be no new 'science' or new diagnoses without people recognizing phenomenon's that repeat time and time again and listening to the experiences of those people.
I always find it strange when people bring 'science' into it and they don't recognise that the exploration part is a huge part of actually getting the answers. Scientific research doesn't just fall out of the sky randomly. If everyone was like you just waiting for it then there would be none.