IOW, only 1% of its membership and 5% of it's clergy are ethnically Greek. Maybe it's just me, but I'm not seeing a problem here, unless it's considered a fundamental part of the mission of the GOC to spread Greek culture in addition to the Gospel.
Far from a problem I think it is an extremely positive development. One of the occasional problems in Orthodoxy (your mileage will vary) is that some jurisdictions (and I have seen this a few times at the parish level too) can put too much emphasis on ethnicity. Ethnocentrism is not as bad as it once was by any means. But one can still run into it here and there. I remember visiting a Russian parish once and there was not a word of English in the liturgy. I kind of got the third degree (who are you and why are you here?). When I explained that I was Orthodox and not Russian they asked if I was Greek and I said no, I’m of Irish descent. Thereafter every one kind of looked at me like I had just landed in a flying saucer and quietly kept their distance.