Weight is going up..and strength..and size. It is visible, and yes the main attribute is the glycogen from potatoes. I agree with you.How do you know you are gaining muscle? Over a short time period of a few weeks it’s generally very difficult to say if you made any gains.
I find that if I reduce protein intake and increase carbs my muscles look way bigger, but it’s just extra water being taken into the muscles.
On fruits only however i was losing strength and size and weight.
I still do not want meat or dairy. The thought of it is not appealing.