I find postprocessdata loaded LDR_LLL1_{1-32} textures, all other textures has the same size 415B except LDR_LLL1_9 which occupys 16MB.
Found out how to reduce this: Go in Player Settings → Quality → Choose the quality setting you are using to build → Async Upload Buffer Size. By default it’s 16mb, even on low. The minimum value seems to be 2mb, still 8x less! Very useful for headless builds.
Cheers