Originally Posted by
Antarius
The likelihood of SCL-DFW in Y being 500 dollars less than SCL-MIA-DFW in J, while possible, is statistically close to zero on the day that the OP booked.
AA is well know for using walk up, full fare Y as their comparison, in which case both routes are probably close, but like the previous statement, the number of people booking walk up, full fare Y is statistically close to zero.
Oh, I agree. I meant to suggest that the direct vs connecting issue may be one of several factors. I think it may be as simple as they calculate the refund as (what you paid) - (what you flew if it was purchased at the time of the change). That calculation is going to be affected by the direct vs connecting issue, in addition to the advance purchase vs walkup fare issue.
Another factor may be how the change was processed. Although the change was triggered by the anticipated SCL-MIA delay, it's possible that it was implemented as a voluntary change as opposed to involuntary due to flight irregularity. If you showed up the at the airport and just wanted to switch to the direct flight for no particular reason, and agreed to the lower cabin, and didn't for whatever reason take advantage of any SDC rules that might apply, what I describe above is exactly how the refund would be calculated.