Interesting to know that there is a performance difference between those categories.
I did also try loading from a CF card into a card slot (not in camera). Same speed issue.
I think it has something to do with the external disk.
I've just created a new catalog on the local SSD from camera and it performed as expected.
Based on the number of responses, seems that I'm the only one experiencing this. I'm thinking it is not LRC.
There are other issues I'm seeing with Lacie 2big disks. When two are plugged into an M1 systen over Thunderbolt, they spontaneously eject. Running just one the issue doesn't occur. Running over USB 3.1 seems to be more stable. Didn't see this on Intel, but it's been a while since I've run that setup. So I'm now working through disk diagnostics.
The feature that would have been really handy is a transfer rate displayed somewhere. It would be useful to know how fast LRC is transferring data, you could then make some judgements of where the issue is. And there are two parts to this camera -> computer -> disk. So knowing which side is the bottleneck would be useful. Knowing that there is a significant change in disk performance might signal that its time to buy a new drive or do some maintenance.