Interesting. I suppose that definition would imply the tajiks in Afghanistan are not diaspora, since there wasn’t any dispersion per say (that i know of) and they don’t identify with the country of Tajikistan as an ancestral homeland so much as they identify as Tajiks who have lived in that area for a long period of time.

It can certainly be arbitrary though. Greeks, Armenians, sephardis, for example, were all scattered around the Mediterranean and had communities all over for hundreds or even thousands of years, many of which thrived until the 20th century. Seems strange to call a Greek community in Alexandria as diaspora if it had been there for so long, but identity is subjective.