After some testing with the new HWInfo64 version 6.42, we've validated these same high VRAM temperatures that Igor discovered. Looping Metro Exodus at 4K Ultra settings for several minutes on an RTX 3080 Founders Edition allowed the GDDR6X modules to hit a peak temperature of 102C. The TJmax for GDDR6X is 95C.
However, this changes when enabling DLSS and Ray Tracing. The RTX 3080 with Metro Exodus at the same settings hit a peak temperature of 94C. We also tested an RTX 3090 Founders Edition in Cyberpunk 2077 with DLSS and Ray Tracing enabled. GDDR6X temperatures for that card peaked at 100C.