Salamun Alaikum.
The expectation of its inclusion is respectfully unwarranted in my humble opinion.
Please see the qualification 'wa-quli' in 27:93 with the conjunction 'wa' (and) which clearly implies the 'qul' in 27:91 when read in context. This style of narrative is not atypical when a particular audience or speaker is implied. There are also other examples where a particular speaker is implied but not stated. For example, who is the implied speaker in 19:64 or 37:164-6? Though not stated, it is clearly implied.
This, along with other examples of sudden pronominal shifts is a very powerful discourse style / rhetorical device which the Quran utilises as a narrative technique. Unfortunately, though translations are good to obtain the gist of the message, they can never fully (nor do they always intend to) capture the 'colour' of the Quranic dialogue. The Quran’s narrative style in its classical remit has its own place in linguistic studies within Quranic scholarship and a special appreciation to the native (or well versed) Arabic-speaking listener.
We need to be clear what we intend to study or debate. The Quran's underlying message or the Quranic discourse style?
Each albeit with overlaps, has its own place.
I hope that helps, God willing,
Joseph