I think it doesn't matter. Losing RNH, possibly Huberdeau and Hamilton would be a disaster whether they're wearing a letter or not.
Because he's played in the NHL, was the first overall pick etc. he's going to be looked up to and counted on. Was the easy decision.
Doubt there is a "handshake deal" in place... Hockey Canada wouldn't let that happen. The reason Zibanejad isn't going is two fold... 1. He already won a gold medal last year, scoring the OT goal 2. He needs to adjust to the NA game
RNH was cut two years ago and has unfinished business... this is likely something he wanted.
He definitely wanted it but did the Oilers is a bit of a different question. Canada's first two games are against Germany and Slovakia - are games like that considered detrimental to his development? He's missing a month and a half in a league that is very good for his development. Wearing the C is great for him and so is representing his country and potentially winning a gold medal at this tournament but do the pros outweigh the cons if you're in the Oilers brass?