Despite the release notes, if CineBench R20 is using AVX, Maxon sure is hiding it well. I just ran a 5 GHz run on my i9-7900X and did not see any offset activating, and I would know, since my offset is -10.
4.5 GHz core + 3.0 GHz uncore = 5917
4.8 GHz core + 3.2 GHz uncore = 6297
5.0 GHz core + 3.2 GHz uncore = 6555
R20 uses a lot more power than R15 though. It actually produces a higher temperature than Prime95 here, despite lower overall power. I saw thermal throttling at my custom Tjmax (85 C) once my liquid temperature reached 27 C, which is harsher than Prime95. To get the 6555 score, I had to wait about half an hour for my liquid temperature to settle at 20 C.
EDIT: I disassembled Cinebench.exe and found it only uses 128-bit AVX instructions. However, it does execute FMAs, which explains why the thermal density is worse than Prime95 26.6 (128-bit non-FMA).
The top function in R20 (embree.dll):
vmovups xmm0, xmmword ptr [r11+rsi*1+0x20]
vmovups xmm2, xmmword ptr [rdx+rsi*1+0x20]
vmovups xmm3, xmmword ptr [rax+rsi*1+0x20]
vmovups xmm4, xmmword ptr [r15+rsi*1+0x20]
vmovups xmm5, xmmword ptr [r14+rsi*1+0x20]
vmovups xmm5, xmmword ptr [r13+rsi*1+0x20]
vfmsub213ps xmm0, xmm13, xmm9
vfmsub213ps xmm2, xmm12, xmm10
vfmsub213ps xmm3, xmm8, xmm11
vfmsub213ps xmm4, xmm13, xmm9
vfmsub213ps xmm5, xmm12, xmm10
vfmsub213ps xmm1, xmm8, xmm11
vpmaxsd xmm0, xmm0, xmm2
vpmaxsd xmm3, xmm3, xmm7
vpminsd xmm4, xmm4, xmm5
vpminsd xmm5, xmm1, xmm6
vpmaxsd xmm0, xmm0, xmm3
vpminsd xmm0, xmm0, xmm3
vpcmpgtd xmm0, xmm0, xmm3
vmovmskps edi, xmm0
xor rdi, 0xf
Outside of Embree, the Cinema4D code itself only executes scalar instructions.
Edit2: Turns out my cooling problems were because I had no exhaust fans. After adding 700 rpm exhaust (X299 DARK doesn't support fan curves for case fans, ***!), I can consistently complete one run of R20 without throttling.