Grid/3D has been always true by default. Is it explicitly set in your launch file? Here are the parameters different from defaults:
rtabmap-info --diff f8d615c7-587b-47d5-80bb-b15764e18271.db
Parameters (Yellow=modified, Red=old parameter not used anymore, NA=not in database):
Grid/3D= false (default=true)
Grid/RangeMax= 0 (default=5.0)
Grid/Sensor= 0 (default=1)
Icp/CorrespondenceRatio= 0.2 (default=0.1)
Icp/Epsilon= 0.001 (default=0)
Icp/Iterations= 10 (default=30)
Icp/MaxCorrespondenceDistance= 1 (default=0.1)
Icp/MaxTranslation= 2 (default=0.2)
Icp/OutlierRatio= 0.7 (default=0.85)
Icp/PointToPlaneK= 20 (default=5)
Icp/RangeMin= 1 (default=0)
Kp/MinDepth= 1 (default=0)
Mem/IntermediateNodeDataKept= true (default=false)
Mem/LaserScanNormalK= 20 (default=0)
Optimizer/Epsilon= 0.0 (default=0.00001)
Optimizer/Strategy= 1 (default=2)
RGBD/AngularUpdate= 0.05 (default=0.1)
RGBD/LinearUpdate= 0 (default=0.1)
RGBD/LocalBundleOnLoopClosure= true (default=false)
RGBD/NeighborLinkRefining= true (default=false)
RGBD/ProximityBySpace= false (default=true)
RGBD/ProximityGlobalScanMap= true (default=false)
RGBD/ProximityOdomGuess= true (default=false)
RGBD/ProximityPathMaxNeighbors= 1 (default=0)
Reg/Strategy= 1 (default=0)
Rtabmap/CreateIntermediateNodes= true (default=false)
Vis/MinDepth= 1 (default=0)
Grid/RangeMax and Grid/Sensor would be modified from the default if a scan or scan_cloud topic is subscribed (and a log/warning is shown on start telling so).