staking PMMP is a special application of PMMP specifically for liquid staking that requires some static parameters to be changed. Interest rate parameters have been updated for the fact that liquid staking derivatives and their underlying native tokens have much lower volatility than they would in other cases.
Three constants (kink, multiplier, and jumpMultiplier) have been changed in JumpRate.sol which therefore caused the Lendgine.sol creation code hash to be different. Other than that the codebases are identical. No audit has been performed on stPMMP.