Getting rid of multiplexing is a result of having a high number of IO pins: an MCU like the STM32F429BE also has enough pin for direct-attach switches. Ghosting hasn't been an issue for ages, even with a traditional keyboard matrix it's just a matter of adding per-key diodes.
In theory it has a sliiightly lower latency than an MCU-based keyboard using the same USB interface, but I doubt the difference is big enough to even be measurable in real-world scenarios. We're talking about, at most, a few thousand cycles of an MCU running at a few hundred megahertz - and that's only relevant when you press the key right before a polling request arrives. That's the difference between an average input latency of 0.500 ms and 0.505 ms. Meanwhile on the output side, your fancy 480Hz monitor is only showing one frame every 2.1 milliseconds...