After Yamao's utterly underwhelming df reveal people were still holding out for her full zoan form reveal to be a moment that wasn't
completely half assed. But Oda decided to make that moment an even more forgettable, every day occurrence. xD The only striking thing about it being how fucking hideous that canine rat looks.
It's extremely clear which transformation Oda was far, far more invested in making a big deal.
One's given all the significance of a future straw hat's first power reveal. The other literally couldn't be more bare bones if Oda tried.
The only interesting thing that come out Yamao's transformation is the similarity to another dog we've seen this arc.
Ushimaru was a Wano lord and he travelled around with a trusty canine companion at his side. This could be a nice parallel to Momo, future shogun, travelling around with his own canine in Yamao.
Just visually, Yamao and Onimaru are already extremely similar so I wonder if this was done intentionally. Not to mention that Yamao actually met Ushimaru in the cave and he looked after her.