It's plausible. in some crosses, I get seedlings with man, many quilled petals, which is a dominant trait in Sunblest seedlings. I had a ton of Toprose x Baby Love that did exactly this.
It's interesting, because Coalite is such an obscure UK rose, so you know the tag wasn't simply at random.
The only problem is that Sweet Magic is often set alone as the sole female parent in legal works. Which makes me wonder if it was Sweet Magic x (Sunblest x (Chinatown x Rosa davidii elongata)).
The secondary problem is that Baby Love is triploid, and I am guessing it is because Sweet Magic is triploid. It is possible that triploidy was generated twice, but I'm going to hazard that it was passed on once.
