Contactei o consulado da Grécia sobre esta questão. A resposta do consulado grego foi:
Consulate General of Greece in New York 11:28 am (1 day ago)
I understand the problem now. You should contact the Consulate that issued the visa. He might have a problem if he continuously stays in Schengen.
Sincerely, Consulate General of Greece
Sent: Τρίτη, 4 Φεβρουαρίου 2014 1:30 μμ
To: Consulate General of Greece in New York
Subject: RE: Visa Question
I apologize may be I didn't make it clear the question is actually whether he can remain continuously in Schengen area.
On Feb 4, 2014 12:54 PM, "Consulate General of Greece in New York" wrote:
If the visa is valid then he can use it. You should contact the Consulate that issued the visa as well.
Consulate General of Greece
Sent: Δευτέρα, 3 Φεβρουαρίου 2014 10:03 μμ
Subject: Visa Question
I have a friend who has 2 short term visas granted to me which turned out to be consecutive single entry visas.
Namely, One visa ends on May 2nd and the other begins on May 3rd. How he managed to achieve this I am not sure.
He has a question on whether or not he can continuously remain in Schengen area and what he will need to do to update the information?
He is arriving to Germany on April 19th for the first time in years.
Meu palpite com base nos comentários recebidos dos consulados da Alemanha e da Grécia é que vistos consecutivos são uma raridade ou não devem ser emitidos.
Tendo em conta que estou a responder após os dias de visita pretendidos, pode querer adicionar o que realmente fez.