I don't think it takes away from the show/performance, me not knowing a song or where its from doesn't take away from how well they performed it/ how good it is, not knowing that the song Fauna sang was Watame's original wouldn't have affected what i thought of Fauna's performance.
Sure if its a song that has some nostalgia value or deeper connection, like if Sana had a song and Ina sang that at the first EN live, that may earn some bonus points but that's like adding 5 extra points on a test worth 500. Its not gonna make a bad performance good and if its all ready a good performance it doesn't need it.
The bigger mistake is not having Gura and Kronies new songs ready for release soon after the concert, this is the moment that they have the most anticipation, if it takes 2 months for them to get released then bootleg copies clipped from the concert will all ready be all over the internet and the official releases won't have the same impact, and we know that deep down all entertainers are at least a little bit numberfags.