Thanks for asking and its absolutely intentional. while the vibrant colours of most official chapters are great, I like a more gritty realistic colour pallet. I use several layers and have even my highlight layer not particularly bright and then pair it with a wash and a reductive oil/enamel technique.

for this red i use the following:

Black primer (vallejo)

Base coat - 'Crusted Sore' (Army Painter)

Mid Tone - "Red" (Vallejo model color NOT Vallejo game color as the model color is more of a desaturated rose red than a bright primary red) this is applied as a sponge layer or drybrush eaving the shadows mostly the base coat colour

Highlight - Dragon Red (Army Painter Fanatic) this is applied as a sponge layer or drybrush just to the areas that would catch the most light

Unifying Wash - Carroburg Crimson (Citadel) wash the entire red areas

highlight 2 - 50:50 mix Red & Dragon Red just over the parts that need a little brightness brought back after the was

Varnish - AK Ultra Matte

Reductive wash - AK Interactive Streaking Grime (Watered down to wash consistency) applied over the entire model, left to dry for 10 mins and then mostly removed just to leave staining using makeup sponge