To define a mobile device, we use the standard wp_is_mobile WordPress function, it seems that it cannot define your device as a mobile device, therefore it shows desktop content unfortunately we do not have a solution on how to include your device in the mobile list.
I found a fix for this problem. I am sharing the link with you from WP Rocket documentation. It turns out their mobile cache does not include tablets, therefore they have a “helper plugin” to fix this.
I just thought I would share it with you incase one of your customers complain about the problem, now you will have a solution for them.
Also maybe you can consider adding this to your demo site. When I checked your demo site on tablet like you asked me to, it looked like the caching wasnt working there either.