A Oneplus device with the model number "OnePlus GM1905" is floating around Geekbench with the specifications indicating towards a Snapdragon 636 SoC. With the Oneplus Z hanging around the corner and launch dates cornering towards next month, you may be completely freaking out right now. Stop right now 'cause, the benchmark isn't from the Oneplus Z or any real Oneplus device for that matter.
It may come as a surprise to you but, Custom ROM developers can easily fabricate results like this by altering the system properties in their code. A very similar incident took place with the Geekbench score of a device called POCO F1 Lite with the code name "uranus" which, as you already know, doesn't really exist. People were going bonkers about that benchmark but, that result was set up on purpose. This was confirmed by XDA Developers and in the same article, they also showcased how that was easy to achieve with some of their own results, fabricated using a Pixel 2 XL.
Developers mostly fabricate results like this for fun. They want to make you exited about a device that does not exist or in this case, want you to freak out over a hyped upcoming device having bad internals. Oneplus knows that if they launch any device with an under-powered or a backdated processor, they aren't selling it. Remember the Oneplus X? The above benchmark is from a smartphone running on the Snapdragon 636 but, it sure isn't a Oneplus device. Also, multiple indicators suggest that the model GM1905 may actually be a regional variant of the regular Oneplus 7.
As previous leaks indicated the Oneplus Z will likely arrive with a Snapdragon 765, 6GB RAM, 128 GB storage & sub-6 5G support. It may also spot a 64MP main camera, a 90 Hz Super-AMOLED Display and the same Warp Charge 30T like the Oneplus 8 series.