Actually, I can see from the picture on their site that the leaves DO differ, but it's too early for a comparison (I'm just getting teeny leaves on it now). Is it normal for them to sprout leaves so late in the season?

Well, you know it isn't the one labeled Fragrant. That would be leafed out long ago and it has the typical heart shape leaf.
The other variety is much more unusual so I don't know if you'll get a poster who grows it here on the Upstate forum. You could try the Shrub Forum. When asking over there, use the Latin names and/or link to the Arbor Day site.
I do wonder about any lilac leafing out this late. It makes me wonder if you actually got something completely wrong. A photo would help.
Remy

Here is a link that might be useful: Arbor Day Lilacs