I went to the local dealer to inquire and was informed i need to replace the entire panel to get that seal which has rotten. And the panel comes unpainted as well! What a hassle just for a strip of rubber.
I have the same issue on my 2009 FSTI and new to me 2010 Outback 3.6. I'm going to try removing the panel and cleaning off the old gasket material then using silicone for a new seal. That trim piece is $200+
Ask for this part. I replaced mine with the panel in place using a plastic trim panel tool that has a 45° angel on one end. If I had to do it again I would remove the panel to replace it. It would be much more easy to get the old double stick tape glue and set the new strip in place.
As shown, it is available separately. The trick is removing the rear garnish or hatch cover without breaking anything.
Btw, any water that goes past that seal just drains right out without ever going into the cavity of the hatch. It all stays outside.