(For potential link rot purposes, this is Shiori and Yuhane's Bday performances of Suki tte Itte yo juxtaposed side by side.)
Sometimes songs are really written for group singing (the same melodic phrases repeated, only differentiated by the timbre of the singer changing from line to line), and other songs work better as solo songs (where the singer can portray a lyrical turn from line to line).
Given that modern H!P doesn't do soloists, the line can be blurred. What this video shows, though, is that Suki tte Itte yo, and a fair amount of other Juice=Juice songs, are very much soloist-inclined songs. The melodies travel over longer "distances", giving the singer arcs to portray. It's got that diva swag. I could easily see a world in which this was a Goto Maki song.