It's an architectural design choice; there is performance loss when you have unused CPU cores, but you gain more performance in tasks that do scale. Hence, "Game Mode".
So they choose to excel in productivity workloads while taking a hit to gaming? That's a choice they made? As in they could have went the other way around and made better gaming CPUs? Or, is that just happened to be where their R&D landed them?
*Because I am somewhat biased against AMD even with the Ryzen CPUs because I mostly game and I continuously see their CPUs with many cores being underutilized AND bottle-necking top-end GPUs. (talking about their mid-range Ryzen 5 mostly)