The difference between FF600R17ME4BOSA1 and FF600R17ME4PBOSA1 is the addition of the P suffix. The parts with the P suffix include Pre-applied Thermal Interface Material (TIM).
For more information on Pre-applied TIM see application note Infineon-AN2012_07_Modules_with_pre_applied_Thermal_Interface_Material-AN-v02_01-EN.pdf