Can't read the link (browsing on my phone, which makes jumping around links more bother than it's worth!) but I'm pretty sure I know what you're getting at.

It's a good question. Purely hypothesising, I could imagine that the immediate benefit received during the sessions reinforces the idea that the acupuncture is 'working'. And it's well known that pain responds strongly to expectation and placebo. So we might imagine that acupuncture, presented as a long-term solution, has only short-term objective effects (through gate control) but this carries over into a subjective long-term response (through placebo).