They can totally fit Nvidia GPUs, just not particularly high performance ones. It's not that hard to find a thin-and-light laptop with a low powered discrete Nvidia GPU.
Heck, even the Switch technically has an Nvidia GPU.
I don't think you read the full details. The Asus Flow convertible is a tablet/laptop that supports a full desktop external GPU, in addition the discrete mobile GPU that is built into the device.
