Applying new propagation method to Super Table blocks generates duplicates

[bmilagre]

Describe the bug

We have found out for some fields that their propagation method has been set incorrectly. After changing the method from "Only save blocks to the site they were created in" to "Save blocks to other sites in the same site group", the already created entries get contents from the other language (site).

Our website has several sites that are used as a language. All languages are linked to the group. One entry should be filled first and then duplicated for the other language.

Content from language DE before propagation change

Content from language FR before propagation change

Content from language DE and FR after propagation change

Steps to reproduce

1. Create supertable field with table layout and some text fields as children with the propagation type of "Only save blocks to the site they were created in"
2. Add the field to an new entry and fill it.
3. Add/switch to the desired different site
4. Change the content of the field to see the difference
5. Change the propagation type to "Save blocks to other sites in the same site group"
6. Open the created entry from 2

Craft CMS version

4.3.6.1

Plugin version

3.0.7

Multi-site?

Yes

Additional context

It is a little complicated to explain that simple without proper content. The steps above are not quite identical to mine as I am applying the config from the colleague who did the customization of fields.