That would strongly depend on the material. Is your material subject to crevice corrosion or stress corrosion cracking? Theses create crevices and don't always share load evenly.
Would the OP care to clarify the specific application as the focus on ASME B31.3, 314 seems to be more for threaded joints as opposed to the indication of injection quills where even hydraulic fittings may contain some threaded components that will not be avoided in any service.
Op,
20% H2S service will fall under Category M Fluid. Refer to Chapter VIII Part 4 and go from there.
Threaded connections can't be avoided in any category fluid but the Code provides limitations and specific rules for Severe Cyclic Condition and Cat M fluid.
It sounds that the joint connection of the injection quill in the example isn’t complied with your company piping spec of the H2S service. Or, are these threaded joints in the existed piping from the ancient plant?
There are many lessons learnt regarding the H2S incident or the leaking of the piping threaded joint. It’s really sad to learn the incident of the H2S leaking through a threaded joint again.