Hello, there, this answer is coming 4 months later. I just happen to run accross it. FYI, the cropping/splicing tool was not designed to create single frame animations when removing frames. That tool is for splicing/cropping out multiple animations from a ‘single’ animation frame. I created a video tutorial on my YT below and I discuss what tool is available to create a ‘crop or splice’ out a single frame animation from another animation in Unreal Engine 5.
Also, here is a link to my Udemy course where we cover this material in detail.
Cheers.