"The kālua pig is delicious."
Translation:ʻOno ka puaʻa kālua.
Pukui et al. differentiated between 'normal fast speech' and 'slow speech of careful speakers'. I expect DLHawaiian wants us to be in the second group.
Native speakers certainly do shorten "puaʻa" to "puʻa" at times, and this kind of shortening can happen with other words as well, such as "loaʻa" -> "loʻa".
Ah, I see. That's a good question, and I do not know the answer. I cannot say that I recall definitely hearing "puʻa kālua" in speech, but I also do not know that it is never said that way. I am inclined to think that there is no reason that it could not be shortened in speech.