XPS 13 9300 Throttling as battery goes lower + with USB device

I've been using the XPS 13 9300 (13", 1065G7, FHD) and while this machine is formidable and powerful on AC, it's performing fast on battery until around 75%. After that it starts reducing the performance more and more. For instance, at around 50%, the maximum CPU power allowed is 14 watts, and when you plug in an USB device (like a mouse) it goes down to 10 Watts.

At that point, the machine is twice as slow as under normal conditions. I feel it's inappropriate that an expensive machine with such a powerful CPU is reduced to half its speed? Also what's the point of such a portable machine if it can't really be used at reasonable power on battery?

While I appreciate the consideration for the battery life, could Dell add a switch in the BIOS to prevent these limitations?

Note: It happens both on Linux and on Windows, even with the thermal management set to "Ultra performance" in Dell's Power Manager.