I'm baffled at how many people don't understand what an easter egg is. They are very common, and tons of series like to do it. Especially long running series like Naruto/HxH/Bleach/DC, you can find *dozens* of eggs tjere, mot just oneor two
Pplus for the theory crackpots, this was half way into *part 1* canon. Did we even know Rins name, or anything about here then? I don't think so.