Phosphatidylglycerophosphate phosphatase involved in the biosynthesis of phosphatidylglycerol (PG), a phosphoglycerolipid predominantly present in chloroplastic thylakoid membranes and which has important photosynthetic function (PubMed:25910650). Required for thylakoid membranes development and chloroplast function (By similarity). 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycero-3'-phosphate) + H2O = 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) + phosphate Phospholipid metabolism; phosphatidylglycerol biosynthesis; phosphatidylglycerol from CDP-diacylglycerol: step 2/2. Belongs to the HAD-like hydrolase superfamily.