There's nothing weird about it. It's an oxygen/ventilation-related problem. What is insufficient oxygen content to one person is not insufficient to someone else. It is not the experience of one young healthy man that determines the quality of the cabin air aboard the 777. It is the accumulated reports, empirical and anecdotal, of many passengers not so sturdy, world-wide since its inception, that points the finger at the air quality in the cabin.
Naturally, the longer one is in that environment, such as on the Kaula Lumpur route, the greater the chance of developing mild symptoms of what amounts to hypoxia. And since the crew use more oxygen walking up and down the aisles than the passengers, they would report a higher rate of these mild symptoms. The reports of ill health from cabin crew are legion.
Note that cockpit crew have not been known to report any of these symptoms. And no wonder. The cockpit on every airliner is constantly fed a supply of freshly compressed air from outside. They breath no recycled air. Airliners have this design to keep the pilots' brains well fed. For obvious reasons.
Why don't they give the cabin 100% fresh air too? Because bleeding compressed air off the engines bleeds compressed air that the engines use to produce thrust. Which means that more fuel must be consumed to make up for that luxury of bleeding freshly compressed air to maintain a 100% fresh air cabin. It's cheaper to filter and recycle it, maintaining an optimum ratio of fresh air to recycled air that meets the needs of the average person sitting down. Some people's needs are greater that what this ratio allows. Thus the reports.
The 777, being of ultra-modern design, is evidently also ultra-economical.
Nothing weird about that. Makes cents