Barrels generally don’t care to be restrained. Mess with barrel harmonics and accuracy generally suffers.
I don’t care for the gap between a pickup bed and the cab. If it were not there, the shert metal would become distorted, buckled and limit frame flex as designed. This mount is the same way. It is engineered to allow it to not place undue stressors upon the barrel.
If it bothers you that much, sell it and TRY to find a better mount.