Why does data-isso-id need to be written twice?

[flux77]

According to the documentation at https://isso-comments.de/docs/reference/client-config/?highlight=data-isso-id, there are two places where data-isso-id could be written: in the <script> tag, or in the tag containing the comments (i.e. #isso-thread). The documentation for data-isso-id was added in commit 30f0c7eeb895163339d3515fc15f6d408137fee6. Why are there two places to write data-isso-id?

I noticed that the embed script will only use the data-isso-id that is in #isso-thread (reference: https://github.com/posativ/isso/blob/0.13.0/isso/js/embed.js#L125), so what is the use of the data-isso-id in the <script> tag?