My thought as well, but the question is: does it matter for what the survey is trying to achieve?

Some people will interpret it one way, some a subtly different way, but is there a reason that people's interpretation changes over time in a way that is more rapid and more significant than the underlying question of how good their life is broadly? Probably not.

There may be cultural differences that make it tricky to do comparisons between cultures / countries, but it should give something useful when looking at the same culture / country over time.