This is a bit cliché, but while listening to the podcast they mentioned the air/water tribe being religious. They also mentioned that one of the two believed in the toa. Two ideas came to mind, one is a call back to Mystery of Metru Nui where the matoren did not believe that Vakama and the others became toa and that something similar could happen. Example:
Jalla-Narmoto, why did you paint all of your armor red? Cosplay?
Tahu- What, noo! I have been chosen by Iker to be a toa.
Jalla- (Bursts out laughing) Oh forgive me, I did not think that my friend was so imaginative.
Something like that, I don’t want Tahu to have that “am I meant for this” ark, but I thought that it would be a good example. Another could be that Ekimu and Makuta remark that the toa look different than the original six, but are startled when they meet Voriki. Again, I know this is cliché but it is a thought.