Why do certain Blu-rays have DVD (SD) scenes mixed into them?

I was re-watching one of my favorite movies Batman: Mystery of the Batwoman. When I started to notice that certain scenes would play in DVD (SD) quality while others were in Blu-ray (HD). I do not know how well the quality difference shows up so I marked each photo.

It didn't detract from the viewing experience but it was distracting when the quality would suddenly drop from HD to SD. This is not the first time I have seen this either. On the recently produced Blu-ray copy of Kanokon, there were entire sequences that were not HD but SD interlaced.

Does anyone know why this happens? Did they not have access to the original material?

Thanks for taking the time to read my post and responding.

Source of photos is from Batman 80th Anniversary 18-Film collection (UPC#: 883929681266)