Strange database design

I noticed that the 'product' table has a foreign key 'image_id' pointing to the 'image' table (one-to-one or many-to-one relationship). However, there is also a 'product_to_image' table for implementing a many-to-many relationship between 'product' and 'image' tables. Doesn't the latter make the 'image_id' field in the 'product' table obsolete?

I assume that a product can have one or more images, and that an image can be shared by multiple products.

it could be that the image_id in the products table points to the default image... I do not know this for sure... but that is a solution that is sometimes used in database design

One is the main product image and the others are additional images.