This image was created to show how air flows through this newly designed fan unit. Many layers and transparencies were used.
I can understand that. I work at a large electrical sign company designing signs and graphics and I get art/logo files from all over the country. Most vector files are generated in illustrator and are a constant source of headaches since we use Corel Draw here. When I enlarge those files up for large format printing the outlines do not scale up with them and the corners on get clipped off since everyone is using fake outlines on them. The blends are always opening corrupted.
Even though we have Adobe Illustrator here just so we can open them in their native software, I still must re-work those files before we can print them. So it makes sense they would want the files that way.
So, this illustration would not be accepted by, say, a site like istock?