I have the same problem with the fob in my pocket; the rear gate button gets pressed unintentionally. Numerous times the gate has been opened with the vehicle in the garage. Not being aware that the gate is partly opened and wedged against the garage door, I have activated the electric garage door opener. The result is scratches on the rear hatch and use of the touchup paint given to me by the dealer when I purchased the 2019 Ascent.
Possible Solutions: 1. Owner's Manual page 153 says, "The operational/non-operational setting of the remote power rear gate opening function using the access key fob or transmitter can be changed by your SUBARU dealer. Contact your dealer for details." I have not done this yet, and I have not seen DIY instructions, which would probably not be a wise act for preserving the vehicle warranty. I would like to disable the function of the rear gate button on the fob. 2. Another solution might be to make or find a hard plastic case that intimately fits the fob so as not to expand bulk and that protects the buttons. The case could have a hinged or sliding door. I rarely use the buttons. Pre-Ascent, I had a 2005 4runner with a manual gate and a small fob for unlocking doors and a key which also unlocked doors and started the engine; that was just fine. Does anyone have other ideas besides the above items 1 & 2 or carrying a pocketbook?