The real devaluation is the one-stop on intra-Asia flights.

Starlux did this with ill intend. Lots of people applied for the co-branded card earlier this year and they are about to accumulate enough miles to exchange that 4 segment flight from Northeast Asia to Southeast Asia. The devaluation came in less than an annual cycle of the card. This is also on a 14 day notice (actually less if you consider the holidays) and sent at 6pm after CSR are already off work with many of the co-branded cardholders billing date already ended this month. The earliest date for billing date next month is the 3rd, so no way for most people to accumulate enough miles to top up. Those who have their closing dates on the next week or so will also need to attain enough miles within the next few days of shopping spree.

With very few partners Starlux has besides the co-branded credit card, the only way to actually get enough miles would be to fly them.

Even BR and CI are better at this with 1 month notice (and CX with 3 months notice).