In the quoted email, it is stated that to "ensure a fair process, [the OSI] must adhere to the deadline for all candidates". I'm not sure what the OSI or their stakeholders have to gain by rejecting nominations for the sake of the few hours that result from timezone differences. The purpose of a deadline is to provide enough time to vet submissions to remove candidates who are ineligible or insincere, clear up any confusion stemming from mistakes in the submission and so on. It's not a race!