Testing for VOC

Legally, based on the ITTF rules, yes. But is it true physically or chemically? 

We know (by smell) approximately what booster each ESN rubber uses fresh out of the package (for example). Say, Bluestorm Z1 uses TRF booster. My opponent has brand new Bluestorm Z1 on his FH (total thickness = 4mm) in a tournament in which expensive VOC detection is not done, but inexpensive thickness detection is. Say, I don't have much money. I have 3 month old Z1 (so maybe 50% booster evaporated away). I boost that using TRF to 4mm thickness. Now, I have only replenished evaporated booster. But my topsheet is old (so, opponent still has advantage). I cannot boost further (shall fail thickness test).

Then, how is my rubber physically or chemically more enhanced vs that of my opponent?

Equipment companies are sponsors / benefactors to both the ITTF and also (surreptitiously) to its management. Hence, it is in the ITTF's interest that you buy as much new equipment as possible. Hence their rules (Donic can boost, I cannot).

If we lived only in a world of Mark V and Sriver, then you would be right in that a player boosting would have an edge.

However, in today's world of Rhyzers and Tenergy, boosters don't enable cheating (in the physical or chemical sense) - as new rubbers come pre-boosted to max 4mm thickness. Instead, you can look at them as the Great Economic Equalizer - that help the poor compete with the rich in a slightly more equal footing (something that the ITTF does not want to enable).

2014-2018, ca 154 infractions, only 21 for VOC, 3 not in LARC or similar, 130 thickness/flatness!!

Thickness/flatness-test seems to be quite effective to keep the racket coverings inside the limits.

I am really not sure if the old ENEZ exist anymore. Fatts idea is interesting, at least to detect VOC/classic glue. It should be possible to find an affordable machine to test for 5 ppm, to avoid health danger. It will probably not detect boosters. I would think that a national association should be free to implement a test like this, as long as the sanctions are like "you will have to play with your spare racket". For ITTF events it will be different, with the player facing a 12 months suspension after 4 infractions/failures.

However, for fair play I think the flatness/thickness is enough. It levels the playing field, at least to some extent.