I'm curious why they conclude "we predict less change than we will actually experience" from this rather than "we recollect more change than we actually experienced."

The authors were aware of this issue and they addressed it twice in the paper. First, for study 1 (p. 96, column 3):

we compared the magnitudes of the predicted and reported personality changes in our sample to the magnitude of actual personality change observed in an independent sample of 3808 adults,

and found that the intraclass correlation of the reported personality changes in their sample matches the intraclass correlation of the actual personality changes in the independent sample. (This is consistent with memory being reliable, but it is not conclusive evidence.)

Second, (p. 98, column 1):

in study 3 we examined the end of history illusion in a domain in which memory was likely to be highly reliable. Rather than asking reporters to remember how extraverted they had been or how much they had once valued honesty, we asked them to remember simple facts about their strongest preferences, such as the name of their favorite musical band or the name of their best friend.

They found the same effect in study 3 as the one that they found in study 1 (suggesting that faulty memory is not the sole cause of the effect), but Ellenberg (which Qiaochu_Yuan linked to) has a critique of study 3 (as well as other parts of the paper).

I think this is a really good question. I might suppose that people intuitively trust memory more than prediction and so when they see the two don't match they assume its the prediction that's wrong.

That said, one thing we know from research is that memory is really unreliable. It removes things , adds details, changes when you tell or hear stories, shifts to fit narratives, etc. I wonder if our instinct here ought to be that if memory and prediction don't match it's because the memory changed and not that the prediction was wrong.

I don't think I've changed that much over the past ten years.

I've gone from believing pretty firmly I was asexual to happily embracing bisexuality. I've picked up smoking and drinking, habits I never would have considered then. I've stopped putting 100% into my work (as a result of my bosses complaining about my productivity, actually - being able to fit forty hours of work for a relatively bright person into two hours is detrimental when you're doing paid-by-the-hour consulting for clients; it's impossible to keep enough work queued up to remain profitable). I've tried recreational drugs, another thing I would never have considered then.

But oddly enough, I don't think my outlooks have changed all that much at all; it's almost all been knowledge. The most sizable change to my outlook has been coming to terms with my own mortality.