In Drupal 10.3, multivalue fields now have a field label.
See the change record at:
New method getLabel() on FieldItemDataDefinition →
This affects TypedData because field labels are shown in the DataFetcher autocomplete. Because TypedData has extensive tests for the DataFetcher, when core Drupal changes the labels like this the TypedData tests will start failing.
Solution is to change the tests so they work in Drupal 10.3+ with the new labels but still work in Drupal 10.2- without the labels.
Fixed
2.0
Data fetcher
Patch taken from @deepakkm in 📌 Drupal 11 release Active