I have a 47 year history in the chemical business, much of which has been involved in polymer chemistry. I have years of formulating and specifying both epoxy and polyurethane coatings, adhesives, sealants & elastomers, aka CASE chemistry. I am now retired.
The Onzow product is very likely to be a elastomeric polyether polyurethane. There would be no need for a fugitive plasticizer in this product as the urethane can be formulated as soft as the Onzow is. Unlike PVC used to produce records that does have a plasticizer. Polyurethanes are reactive 2 component chemistry consisting of the reaction between a Polyol (multifunctional alcohol, think -OH)and as stated it would be a polyether polyol. This is reacted with an aliphatic isocyanate to form the clear water-white polyurethane. This reaction is Not Reversible. The formula would also likely be over indexed with the Isocyanate. Any excess isocyanate not crosslinkied with the polyol would be further reacted with atmospheric moisture, water is H-OH, so it has the -OH available to react. Therefore, there is no fugitive material available to “gum” up the stylus/cantilever. Now the vinyl records do have additives than can be fugitive that could gum up the works. Without chemical analysis we do know what the deposits are. That needs to be determined before jumping to any conclusions.
In regards to using wet cleaning of styli using alcohol or other solvent based solutions this should not negatively affect the epoxy adhesive used to bond the Diamond to the cantilever. Especially if using the recommended drop of solution. Even direct full immersion would take days, weeks and possibly months to have any deleterious effect and even then removing from immersion it could recover. A correctly formulated epoxy adhesive is resistant to solvents except for the most aggressive types like methyl chloride. No manufacture would use this aggressive of a solvent in a stylus cleaner.
I am currently an Onzow user. I have not noticed any deterioration in sound quality since beginning to use it about 1 year ago. I don't have access to a high resolution microscope to inspect my stylus to see what might be there.
I don't have a dog in the fight, but my chemical curiosity has me wondering what is happening. I await further investigative results to determine what is really going on.