Thumbnails are actually the full size images ?

Dear Rich, All,
As I already mentioned, I love this plugin. I have the below question, though.

When creating a gallery block, it seems that the thumbnails images are actually the original (full size) images (–simply appearing smaller through CSS). Am I right ?

This means all the full size originals have to be loaded, just to show a ‘thumbnail’. This is a waste of bandwidth and slows down page loading.
Would it not make more sense to load a smaller-size image (closer to the size to be rendered) as thumbnail, instead of the the original full size ?

I don’t think this is caused by your plugin, by the way. I think this is more a core Gutenberg issue (as I noticed this behavior with both default Gutenberg gallery OR with your Block Gallery plugin).

Would you have any idea on how to improve this ?

Thanks all for your help. Christophe