I'm really thrown by those results. I'm chiefly interested in performance in Premiere and After Effects... and if those results are accurate, the 16" MacBook Pro is largely keeping up with the Mac Pros. What am I missing?
Shouldn't be much thrown much. Much of this isn't particularly surprising.
The 8 core option for the new Mac Pro only Turbo's up to 4.0 GHz. ( the rest turbo up to 4.4 GHz. ) . In contrast, the maximum CPU option on the MBP 16" Turbo max is 4.5 GHz. So these entry models 'give up' approximately 0.5 GHz on highly single threaded critical section portions of applications.
The moving of large files in and out of the storage system will have an impact with the MBP 16" having 16GB more of RAM ( a substantive portion can either be used by the file system for cache or as workings space for the app).
The GPUs across the MBP 16" is about even if not pushing very hard on OpenCL ( or not much direct Metal). The baseline VRAM here s 8GB and the Navi based GPU in the MBP 16" is the 'newest' of the bunch. (so not particularly greatly hobbled by being a 'mobile' GPU. )
Bump the Mac Pro to 12c and even up (or surpass) the RAM capacities of the MBP 16" and the edge will probably shrink on most of these differences. ( and gap grow where the multiple CPU cores and/or GPU can get some traction on the workload).
Adobe's targeting the lowest common denominator is a bit of a boat anchor here also.
But yes ... in part this is one factor as to why Apple isn't deeply stressed in addressing the "old" $2,500-4,000 range of the Mac Pro. Attach an external display ( and storage and perhaps a eGPU) to the MBP 16" and covering much of the old workload space. ( iMac Pro's 10 core ( Turbo 4.4Ghz ) will do well against the 8 core Mac Pro . Same with iMac Turbo i9 for as long as it can hold the 5.0 Ghz there).
The entry Mac Pro configuration's main value point is the stuff that isn't there ( empty slots to be filed.). bumping CPU , Storage , and RAM one step past those initial setting all get to better performance workstation starting point on general workloads. The entry is a better match to where adding in a card or two allocated to a narrow workload is where there is better "bang for the buck".