That isn’t a big issue, but it should be fixed as it is likely a bug. And I’m unsure if this is intentional but I remember in E2023, The R15 Render pose was set as the RTHRO one as default and if it is a bug it should be fixed by now. It’s been nearly 2 years. But if it’s not a bug, still bring it back. The current one looks bad on my profile.
We have reverted this issue in production. New thumbnails should be generated fine and old thumbnails will be refreshed within a day or two thanks for the report. Let us know if this issue persists.