316L, as well as all other austenitic non-precip hardenable steels, are only hardenable by cold working. Even starting with cold-worked base metal, welding should only lower strength/hardness. Start with solution-annealed 316L and it will most certainly meet NACE MR0175.
As noted by OGMetEngr, the HAZ in a 316L weldment should be assumed to have annealed properties as welded. There is no process that I know of that will "lower the hardness" of 316L in the annealed condition. The hardness, and tensile strength, of the HAZ in a 316L weldment can be increased by mechanical working processes such as planishing or rolling.
Sometimes the welds themselves can be harder than intended.
It depends on C, N, and ferrite content.
Often the welds will get softer when they are properly annealed.
But even in these cases they should be plenty soft for the NACE requirements as welded.