The notion of EE is not well defined. Standard English spoken with a southeastern accent. EE is associated particularly with the lower-middle group that nowadays have access to higher education, although fifty years ago they didn't. If Dutch students manage to sound like any kind of native English speaker, I would encourage that. Better sound Cockney or EE or poshest RP than a thick Dutch accent.
Most linguists refer to it as just a matter of pronunciation.
No, not by my definition. No one has demonstrated that it is in any way specially characteristic of the southeast of England. By my definition that is exactly what they are. This implies that we recognize that many speakers switch between Cockney and EE, and that these categories are not watertight but part of a continuum. That is essentially what I suggest.