Overtime != overwork. You've probably programmed something, at some point, where you were excited to work on it from morning to night? Where you lose track of hours, forget to eat meals and completely in the zone? That could easily be the case with these engineers, working on such a historical project and consequential update.
I have been in that zone for two or three day stretches, but never beyond, and never in sync with a full team. I have experienced two forms of team wide over-time in my career. The first lasted (for me) about seven months, then I quit. I couldn't take in anymore and the project (large team, 150 people) was on fire. That was completely unsustainable. The second form was a periodic event that happened every two years when we released a new silicon design (chip vendor). The day that the first silicon was mounted onto boards began a cycle of ten to twelve days, 14 hours a day, lunch and dinner being one hour status briefings. All hands on deck. At the end of those ten or twelve days, either the silicon was fully validated, or all its known flaws were identified. And everybody on the team took a couple days off to breath. That was sustainable because it was infrequent, planned, and closed ended. I went through four of those cycles. They were exhausting and thrilling at the same time. And thankfully, infrequent and closed ended. There was always a light at the end of the tunnel.
This is a different dynamic than traditional organization. It's decentralized with contributors around the world. You have no idea how much others are working and many are contributing because it's something they're passionate about.
