No, it's not a glitch, it's as intended, unfortunately. When they did the gardening overhaul before Seasons came out, they changed the splicing rules for rare plants. There is now only a 1% chance you'll get the rare plant you desired from splicing. It's my personal opinion and the opinion of others that percentage is WAY too low. I have hopes that the Devs will tweak that to up the percentage at least a little bit. I've yet to get an Orchid from splicing, or a Bird of Paradise for that matter and probably 95% of my Sims have/had gardens spliced for those.
I gave up on trying for Dragonfruit from splicing a long time ago because I can get them consistently while fishing at the pier in Magnolia Promenade. You can also fish them up by going to the middle fishing spot in the very back of Magnolia Blossom park in Willow Creek. Ditto for Birds of Paradise, I stopped trying to splice for them because I can get them at the Romance Festival now. I have managed to get Orchids, once. But not from splicing, from picking the pockets for seeds of Patchy the Scarecrow. That's another good way to get rare seeds. :)