I think that there is considerable confusion about the application of imputed income/funds transfers arising from a recent court decision that the concept of taxing
non - residents based on imputed means was illegal/unconstitutional. It therefore rendered it unclear whether the requirement to transfer funds based on imputed costs calculation was also wrong. This confusion probably also exists within Greek tax offices. This link gives some background http://www.kperrou-ontax.com/1/post/2011/05/non-residents-assumptions-for-the-acquisition-of-income-in-greece-abolished-as-from-1-1-2011.html
(And the judgement itself is a hoot, expressed in the article as "The courts have ruled that the use of assumptions for the determination of the income of an individual is lawful, as long as the assumptions do not result in creating fictitious income for the individual but they are used in order to reveal existing income that is not declared by the taxpayer."). Kafka is alive and well and living in Greece.
Prior to this, cash transfer necessary to demonstrate outside (of Greece) income sources was required, and based on the imputed income asset table. If you look at this link (from Atsalakis, but dated earlier than the Tax Oasis write up), it clearly states so (towards the bottom) http://www.apokoronasourhome.com/pdfs/Tax_liabilities.pdf
If you have sufficient funds, perhaps the safest option would be to make a transfer based on the imputed income calculation. Note that the values increased substantially last year, so you would need to use the current Atsalakis table at http://www.cretanaccountant.gr/tax-liabilities-in-greece-for-non-greek-citizens/
The only thing certain at the moment is that confusion reigns within the Greek tax system regarding residents/non - residents/183 day rule/pensioners/funds transfers/proof of income.