According to Engadget, citing Paul Gerhardt's tweet, "tech spec pages for the new machines reveal that none of them are compatible with external GPUs that connect via Thunderbolt".
The Tame Apple Press claims that only handful of people would need any extra GPU anyway but Apple's support for external graphics cards gave it some extra gaming cachet and informed creative professionals.
As it is there is some anger that the 13-inch MacBook Pro M1 models only include two USB-C ports onboard instead of four. The MBP is limited to 16GB of RAM when some of the more power users might want 32.
All up, anyone who wants any real power will have to look at buying a proper PC for a third of the price, and Apple fans will never do that.