No, I'm asking you what you mean by "It's not dust if the piece they found evenly distributed Al in the matrix was soaked in MEK for hours." which does not seem to make any sense.
If something is dusty, and it is submerged in MEK or mineral spirits or acetone or some other type of thinner, the thinner will wash the dust off the object--especially if it's being agitated. Hence the Al wasn't contamination. Nor was it bound to another element because it was about 3 times as abundant as oxygen where the two are present together. Also, there are clearly places on the fragment where Si is abundant and Al is not and vice versa. Thus the only possibility is that it's elemental Al.
They used MEK to allow any bound particles to be revealed from within the binder. The XEDS maps they made of the tip of the fragment reveal Al over a large portion of the exposed surface of the fragment tip.
If all they did was break open a piece of the chip, do XEDS analysis of it, and found Al, they could not claim it was elemental. However, they did an number of corroborative steps which empirically confirm the existence of elemental Al.
Now, what do you mean by "sufficiently strong empirical evidence"?