In the Amazon product reviews, few people wrote that it doesn't work.
I don't expect this to work in all motherboards because it will be drawing the whole power for the GPUs through a single PCIe slot, there is something similar to this on amazon too that has power cable on it, that should work instead of this, remember, the reason why riser works better is because you have to power it using molex or other
The 4-way splitter is connected to the risers through the USB cable which is for the data connection. Only a small 3V current is sent through the USB cable. You still need to power the risers. These splitter won't work in all motherboards. On some you can only get an extra card. It all depends on how the lanes on the PCI-E slot on the motherboard are configured.