Image sizes “medium-large” bug?

The psac-recent-post-carousel.php file specifies a default image size of “medium-large”. As far as I know, this default size does not exist in wordpress. There is “medium_large”.

This leads to the fact that if you don’t specify the media_size parameter in the shortcode, the image will be used in its original size.

I discovered this when a client’s site had 4k sized background images in the carousel.

Is this a bug, or have I misunderstood something?