Adding new files to Power Query folder, are all old files read again?

Question

I have a folder with CSV-reports, and I am using power query to load/combine and modify these into one spreadsheet. These files don't change.

I am getting new CSV-reports in the same format weekly, and I usually add the new file to the folder with the older files and hit refresh.

But this seems slow to me. I'm beginning to suspect that this refresh process is re-reading all of the older files as well. Or am I mistaken?

If this is the case, is there a way to solve this in a less resource-intensive way? :)