I can't reproduce this. I've checked the generated thumbnail dimensions on disk after making such a change and hitting "Make album" and it does update. Ensure you're not being fooled by the browser's cache.
Ensure you're not being fooled by the browser's cache.
No I checked the properties of the images in the thumbs folder with the Internet Explorer.
You can see it in this album, this index pages was made by deleting the thumbs by hand and you see now the small folder thumbs, while in the 2020 index page you see the old large folder thumbs. (you should view this on a PC or tablet, not on a smartphone).
The folder thumbs of the smartphone version of this album were also made smaller, but this album was made without these problems.