Just to follow on from mine and weldstans comments.
Many welders do not have a clue what the specific base material is - 316,304,321 etc - to them it is just stainless steel and it is welded with the same technique and generally the same parameters.
Filler metal is generally the only difference and if you give a welder a WPS with 308 filler metal there is a strong possibility that is what he will use.