Indeed, some mice have a harder to press mid-button/scroll wheel, but there are some which are easier to press. I have a G700S and the middle click requires greater finger pressure than I'd like,
All the mice I've taken apart have one of several setups:
1. click pressure is controlled by a 'spring' inside a microswitch
2. click pressure is controlled by a tactile switch that is soldered to the PCB
3. click pressure is controlled by a spring that supports the scroll wheel axis or the full assembly
As best as I can tell, your G700s' scroll wheel has... 2 and 3.
You can see it here at 6 minutes into the video.
The tactile switch is the gold disk on the left of the screen, with two springs on each side of it.
You could try replacing those springs with weaker ones.
And/or you could desolder the tactile switch and replace it with one that requires less force to operate.
If it's hardware, there's no reason you should be permanently stuck with some focus group's middle of the road choice.
/tactile switches cost pocket change
//microswitches are expensive when ordered as single pieces, so find a place that already has a thousand of them.