The full paper isn't open so I can only read the abstract, method and results.

The part I take issue with: "lower brain-wide mGlu5 availability may represent a molecular mechanism underlying altered excitatory neurotransmission that has the potential to stratify the heterogeneous autism phenotype."

Seems like the very premise is flawed, though. Searching for a single global identifier for autism would be like if we spent research time trying to find a single global identifier for cancer. Noble effort... Way harder than spending effort on subcategorization into "lung" and "heart" cancers and working on research for detection of those subtypes.

The only good categorization we have in autism now is severity.

The anecdote I always like to share is Temple Grandin.

She was hyper-sensitive to auditory and tactile senses. The cause for this hypersensitivity was cerebellar abnormalities in her brain. Right now, someone who is hypo-sensitive to sound and touch because of different cerebellar development will also be put in the same bucket diagnostically speaking. There's not gonna be any universal way to detect that though...

To quote her directly:

"It would be my number one research priority, but one of the problems we’ve got on studying this, is that one person may have visual sensitivity, another one touch sensitivities, another one, auditory sensitivities. And when you study these, you got to separate them out. You can’t just mix them all together." https://www.sensoryfriendly.net/podcast/understanding-my-aut...