I would like to add that I really do not know if this occurs only with Standard Swahili or (perhaps) this is for other dialects. In the beginning, we can see how the course presents some expressions (as greetings) being more colloquial and other forms being used only with foreigners. Then I would like to know if the familiar or colloquial expressions and perhaps the inclusion of different classes to differentiate meanings are part of Standard Swahili or it is owing to a different acquisition of a Swahili dialect (and this would be also a more communicative way of speech for Waswahili.) ;)
I suppose that learning the language at the basic level and reach additionaly dialects is without sense. For a while I am using dictionaries and other helpful materials almost everytime for hold the clasic form and minimalizate mistakes. I also didn't observe inclusions of lateral dialects but the mistakes - yes. :) For side dialects or coloquial forms will eventualy come the time when I will know well the standard language. :)
No mkunga is a bantu origin word. An eel is also called mkunga in ciNdau and hunga in chiShona.