[macOS Sequoia 15.2] This worked for me at some point, but stopped (possibly as a result of a system update). I’ve restarted and made sure that Show icon preview is toggled on (works with Illustrator files in the same folder). (also posted to Github #834)
I wonder if you have solved the issue. Same happening here.
I don’t think it can be fixed on the user side. The dev team has added it to their Github tracker, though, with a status of “In Progress” and marked as a milestone for v1.3.15-beta1.