You can overclock it yourself with this toolWorks in Android 11 full stable (uploaded in Franco Menager).
However, I believe that the GPU clock speed could be higher than 670 MHz. Relax, these 750 MHz would be fully stable. And even 800 MHz. Maybe the author will consider adding Adreno clocks higher than 670 MHz to the current state of the kernel? e.g. 670, 700, 750 and 800 MHz. Although there is a kernel where you can set 900 MHz on the GPU (SmurfKernel 1.1.0) but here it is not guaranteed 100% stability.
OnePlus 8 12/256 Antutu 8.5.2 scored: