It’s supposed to be like that. 3.3 changes the way images work. Instead of setting a width and height you set a width and aspect ratio:
https://woocommerce.wordpress.com/2017/12/11/wc-3-3-image-size-improvements/
So if you want square cropped images that are 300 pixels wide (for example), set the width to 300 and cropping to 1:1.