If you export swim splits to CSV from GC every length has the same data in it. It's all just copied down from the total and even some of that's wrong.
I haven't used this for quite a while so I can't say when this stopped working.
Here's an example swim:
https://connect.garmin.com/modern/activity/1482991005
And I've hopefully attached the CSV file.
Cheers,
Mark.