Eps does NOT support transparency. It will flatten it into solid colors. If transparency is involved at all with a raster image, if flattened, you may get a sliced up image that is no longer linked but embedded as hundreds of shards (you’ll see each piece in the links palette.) This type of save rarely opens properly even in Illustrator. The stitching you get may or may not print.
As a matter of fact, in Adobe programs, spot colors used with transparency can wreak havoc with many PDF formats as well. Saving as PDF requires knowing what you are doing and if you are trying to preserve any spot colors.
I’ve often wondered about stock eps formats. I don’t use them enough to care all that much. Technically they should be .ai. But .eps is the lowest common denominator for those using stock in things other than Adobewares. If it looks like it has transparency in it, buyer beware.