People were saying the same thing about City Folk, but I tested it out in ACCF and never saw any increased hybrid production. I haven't tested it in New Leaf, but I have serious doubts about it. It's probably just the same rumor getting recycled.
It actually increased my chance of getting white carnations and purple tulips. Of how I use them, they are like fertilizer for my flowers. In fact, I have 30+ purple tulips.