Doesn't have to be a replacement trigger, as you can see with Homura, Human Ascendant [link] there is a death trigger that brings it back to the battlefield "transformed" if you will. Regardless, both rulings work, as either a return to battelfield effect or a replacement effect, just a choice of preferance from there on.
yeah thats because it has to wait in the yard for a turn. your card doesnt, it transforms the second it dies so theres no point to word it the same way as Loyal Cathar
"When ~ would die, instead transform it."
makes it much more concise and gets the point across.
Regardless, both rulings work, as either a return to battelfield effect or a replacement effect, just a choice of preferance from there on.