Lipid phosphatase that specifically dephosphorylates the D-3 position of phosphatidylinositol 3-phosphate and phosphatidylinositol 3,5-bisphosphate, generating phosphatidylinositol and phosphatidylinositol 5-phosphate. . This is the function of Ensembl gene identifier ENSG00000163719 (MTMR14, myotubularin related protein 14).