That's what my results are from that I posted in this thread: https://forums.macrumors.com/threads/2018-mini-3-2ghz-i7-temps.2153133/page-4I would recommend benchmarking with something other than Geekbench and Cinebench. Both tests do not tax the system for very long and thus might hide thermal throttling (or other) issues.
Perhaps something such as Handbrake as it's known to utilize a lot of cores for long periods of time. It's free software anyone can easily download and run. We can find a sample video to download and transcode.
Handbrake is probably the most CPU intensive program I run so for me it's what I test with.