I've never heard anything like that before... I wouldn't recommend trying it though. At ~3000ppm which is a common recommendation many people can't taste the salt... at 5000ppm I think it would taste very salty and would likely increase the corrosive aspects as well. Isn't sea water ~6000ppm?
I think having too much salt increases the conductivity of the water too much and the SWG may shut down to protect itself from over-current. Mine has shut down with a light indicating too much salt when I added some salt to the pool and it hadn't mixed in, yet.
I don't know for sure, but I think the oceans are higher than 10,000 ppm salt.
Running your salt system to the upper limits of the recommended salt range will slightly increase cell life, but not significant to claim any great increases in cell life.
It will allow your power supply to run cooler.
Each manufacturer has their own limits. Most have a high salt limit to protect the power supply from damage.
Increasing the salt level also will NOT increase chlorine production.
Ocean water is about 25K - 40K, depending on geographical location. Most oceans are about 35,000 ppm.
Salt Levels maintained at greater than 6,000 ppm can be corrosive to stainless steel fixtures in contact with the water. i.e. handrails, ladders, light rings, etc.
You willl definately be able to taste the saltiness at that point too.