#2371 James Weldon Johnson

Beginner alert so terminology may be amateurish.

I have several stamps from the late 1980s that all have yellow or slightly brown gum that is glossy and shiny under light. However, #2371 (James Weldon Johnson), the gum is slightly yellow but dull/flat and resembles that of the State Birds and Flowers stamps issued in 1982. Is this normal for #2371 (James Weldon Johnson)? What is the purpose/reasoning for issuing stamps with dull gum?

This issue was indeed printed only with dull gum. I do not know the reasons for the creation of dull gum ... perhaps someone else will chime in with the answer.
Added: A number of U.S. stamps have been printed with both dull gum and shiny gum. For a few of these, the dull gum variety is far more valuable. The ones that come immediately to mind are J94, J95 & O136. Hmmm ... just checked my new 2021 Scott and see that the recently discovered dull gum J92 has finally been listed. No CV is given ... as I recall, they were discovered by an SCF member less than 5 years ago. I think there were only 2 or 3 blocks of 4, but my memory is questionable. Definitely a very rare stamp.