There is a bug with the new flow designer. This issue does not occur with the old flow designer. When fields returned from a dynamic schema are input into an action, and then the flow is saved, the labels suddenly change to the property name instead of the title label. When you go out of the flow after saving it and go back into it, it will continue to not show the correct dynamic field labels.
Here's what it looks like before a save (where the labels are correctly visible):
Here's what it looks like after a flow save (notice how the labels from the dynamic schema are no longer correctly showing):
This can be reproduced by using just Microsoft connectors. Here's how this bug can be re-created:
What's even more concerning is when, after a save, you switch to the old flow designer, it continues to not show the labels correctly. This makes me think it's actually persisting this bad label in the database, which would corrupt customer flows over time if a cleanup job isn't run to retroactively fix this issue. If you had created this flow from the beginning with the old flow designer, this issue does not occur.