Are 南瓜小米粥 (nánguā xiǎomǐ zhōu) and 小米南瓜粥 (xiǎomǐ nánguā zhōu) the same thing?
I think they're different. 

南瓜小米粥 is 小米粥 with 南瓜: as you said, it's millet congee with chunks of pumpkin in genaral.



小米南瓜粥 is 南瓜粥 with 小米; it's more like pumpkin puree, with millet grains.



Of course what the name means indeed largely depends on the restaurant.