A friend bought me a 5 CD album of Jelly Roll for Xmas about 6 years ago. I love all of his compositions and I agree about the two you mention and nostalgia.
No it's not. Eduard Lalo, Emmanuel Chabrier, Claude Debussy and Maurice Ravel all wrote authentic-sounding Spanish music. The Spanish composer Manuel DeFalla said that Debussy's Iberia first revealed the true essence of Spanish music to his own people (paraphrasing).
If it's possible to be nostalgic about an era before one was born, this music evokes such nostalgia.