Sakura, good news! I found why it looks shiny thanks to
thread about SRMA.
"Red (255, 0, 0): A very shiny look; very wet/oily.
Purple (255, 0, 255): A reflective shine; works best with shiny metals.
Green (0, 255, 0): Little to no shine; ideal for matte objects.
This make a lot of sense why the head of erection never appears shiny with SRMA.
All I did was made SRMA texture fully green (0, 255, 0) to remove shine. Default vs No Gloss:
I believe this can be done for uncut SRMA as well. I include file of animation version for you if this is okay.
edit: learning more on srma, ^pure Green (0, 255, 0) made the model too dark toned, most noticeable on dark skin. Original srma's erect glans color (200, 255, 0) is more appropriate for matching and proper brightness imo.
You might have known all this, but noob myself did not. I hope this was helpful to who did not want wet oil effects on their private parts. Excuse my poor english.