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I had the opportunity a couple years ago to test EM6000 "melt in" on hardened finish. About eight months after finishing a guitar with EM6000, the finish lifted along the treble side of the neck. It's the only failure I've seen with EM6000. It appeared that there might have been a problem with adhesion to the z-poxy pore filler.

I finally got around to repairing it about eleven months after the finish was originally applied. I peeled the lifted finish off. I sanded the edges of the original finish to feather them and give a smooth transition into the areas where I removed the lifted finish. I applied new finish to the areas where I removed the old finish and overlapped it onto the old finish. I let it cure for four weeks and did my usual sanding and polishing routine and the repair looked as good as new. No witness lines and the junctions between the original finish and the new finish are completely invisible.

I have guitars going back eleven years with EM6000 on them with no other failures, so this one was really strange. The repair has held up just fine for three years with that guitar being my main player.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Target website makes that claim. That is all I know.

Additional info from Target FAQ:

Do I Need to Sand Between Coats?
No and Yes. EM6000, as well as all other EMTECH™ topcoats, has a unique burn-in property that allows the next/following coat to melt into into itself and chemically bond into and onto the last coat that was applied. The EM6000 Production Lacquer offers 100% burn-in qualities that remain functional regardless of how long ago the last coat was applied. This behavior in EM6000 is very much like nitrocellulose in its functionality. Other EMTECH™ top coats such as EM2000wvx, EM8000cv, 9000sc and EM9300 will also burn-into the last coat applied, however, this functionality begins to lower the further out in time the last coat has had to dry/cure. These coatings will chemically bond to themselves, but this functionality is not called burn-in. Therefore, no- you do not have to sand between each coat to ensure proper adhesion, but you do need to lightly sand between each coat to ensure that all surface defects are removed and do not telegraph through to the next/upper layer of the coat being applied.