Even if this is entirely innocent and the result of someone trying to do the right thing... not a good look. They should honestly accept his candidacy and then revise the submission guidelines to be more specific in the future. To do otherwise makes it look like they're trying to exclude candidates to ensure a pre-selected candidate runs unopposed.
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!
I received an email from OSI on February 14 that clearly indicates UTC. It looks like the message was sent to all OSI members. Did Luke not get this email?
It wouldn't matter anyway as they announced the deadline as 17 February, which would mean midnight local time by default (and should mean midnight AoE, especially for an organisations purporting to be concerned with openness).
It’s an awkward situation for sure and the timezone could have been clearer.
But I also feel like if there’s no timezone for a deadline then you should assume the worst case (which here would be UTC) and make sure you submit before?
The author left it so late that in 95% of the world it was no longer the 17th Feb.
The OSI post that the author links to specifies the voting deadline in GMT (effectively UTC) in the sentence immediately preceding the timeline diagram.
So it can be reasonably inferred that they’re generally using GMT/UTC in the rest of their timeline, rather than AOE, UTC+14 or anything else out of the ordinary.
GMT is a bizarre choice for an international organization based in California, too. GMT isn't used in the summer, and the dates when the time switches from GMT to BST and from PST to PDT aren't the same! That alone has caused confusion in every international organization I've been involved with. At least with UTC one can reasonably expect to use it throughout the entire year.