In a normal case you are in taking from the entire front usually, bringing in cool air to the CPU. That air also cools a portion of the motherboard, initially.
It's definitely less in this form but I don't think it'll be an issue with more expensive motherboards. However it also wasn't that long ago we went through massive VRM issues with many boards from power delivery, temperature issues, etc.
I'm sure they did there testing, but with how much wattage GPUs need to be cooled off these days, dumping that much heat to the CPU socket and surrounding components, with no chance of any cool air, just seems like a bad idea personally