Oh, I guess you aren't using ServerGridEditor?
I checked my ServerGrid.json and mine looks like this:
"OverrideShooterGameModeDefaultGameIni": {
"bDontUseClaimFlags": "1",
"NoClaimFlagDecayPeriodMultiplier": "4",
"bClampHomeServerXP": "0",
"ClampHomeServerXPLevel": "0"
},
That is under the segment/server, NOT the first one that you will see when you open the ServerGrid.json (probably line 18 or roughly).