It lists plenty of other formats you can use so why not try one?
I certainly can I suppose...but did you miss the part in brackets that says "this format is used by FS2004"?
I tried to explain how you could use two sets of textures in different formats to suit EOD & FS9. This is complicating things so it would be much better to start out by using the same textures in both.
And why would the tutorial be telling me to use DXT1 with EOD when its very clear that they don't work?
I have no idea. You would have to ask the author of that tute. I haven't tried any of this but if the tute posted on the EOD site says that DXT1 format cannot be read by EOD then I'm prepared to believe it. FS9 should be able to read any of the other formats listed in the green section on that page so I would try one or more of them. I can investigate further if you wish but think it would be much better if you try these things out for yourself.

Wouldn't I be wasting my time by reformatting the textures? They still wouldn't be showing up.
How do you know that if you're not prepared to try it? It would only take a couple of minutes to convert your textures to another format with DXTBmp. You could have found out for yourself long before I had time to type this reply.