Jack instead of Fi?

I started watching the series again because I miss it, and I started to notice things I didn't before when this show was on the air. Idk if it was coz I was a kid when I watched it and just didn't pick up these things or if I just forgot about them..

But the episode Avatar in season 2 is actually narrated by Jack instead of Fi. I found that strange because out of all the characters Jack is the most skeptic. And throughout the episode they spoke to Fi on the phone while she was away and that reminded me of Chrissy on Three's Company. When they were slowly writing Suzanne Somers out of the show they shortened her scenes to short telephone conversations on another set away from everybody. I know Fi sticks around for a few more episodes but this makes me wonder if this was their way of getting ready to cut her lose too.