The "free" shorty 6607XL will work fine in the Civic. Likely the WM ST filter look up shows the 6607 because they don't have an ST 7317 as a purchase option, so they consolidate/downsize it to the 6607 filter. Many quick lubes do the same, using the (~.75") shorter version 6607 where 7317 is spec size. Otoh, AZ does have the Honda spec size 7317 application in the XL, so they do list that and is accurate for the Civic. That likely explains the difference in the filter look up options.