Apple may have answered a multitude of MacBook Pro-user prayers by restoring the SD card slot to the latest versions of these PCs. However, a growing number of owners claim that the "new" port is running unusually slow compared to adapters or dongles. This issue has reportedly led to replacements for some affected consumers.
https://www.notebookcheck.net/The-new-MacBook-Pro-s-SD-card-reader-is-reported-as-dysfunctional-in-some-units.579957.0.html
Did Apple forget to put in their M-series chip a SD card reader accelerator? Geekbench accelerator is great, but SD card reader accelerator would be more practical.