When I first had Piper and Shade interact (which didn't happen until I moved into an apartment, although I had the two of them prior to this), Shade has always shown interest in Piper, wanting to groom him and hang out. Piper, on the other hand, seemed to not care so much and would just walk away.
As the flock grew, Shade remained the one Poi that seemed the nicest towards Piper. Léa has shown a curious interest towards him as well, but due to size difference, both will never be left out of their cages together.
Years have gone by since that initial move, and slowly, Piper has shown a bit more friendly disposition towards Shade, at times following her around and either trying to mimic what she's doing (playing) or, if I happen to give them treats while out of cage, trying to get to her crumbs and he's the only bird she'll allow to do this.
This morning, Piper was playing with a piece of yucca and Shade showed interest. I gave her a bigger piece and Piper came closer, waiting for smaller pieces to fall close to him so he could chew on them. It was quite cute!
Of course, they are out together under strict supervision, but it's nice to see a kind of friendship form between the two of them.