Okay, this is a stupid rumor for one simple reason, Yoshio Sakamoto was promoted to NCL Development Department Manager back in 2014, this is fact. Tanabe works under Sakamoto now, so do over a dozen producers actually, and Sakamoto oversees more projects now from his promotions from Group Manager (managed 2-3 development teams at a time) to Department Manager (manages a dozen of development teams at a time). Sakamoto will likely be overseeing Federation Force from an executive or senior production position, just like he will be many other games. This doesn’t require much research as it is an ostensible certainty based on his position at the company. But Sakamoto isn’t going to be flying over to Texas to do quarterly checks on the products. There are plenty of traveling producers at NCL who specifically serve that role of international producers, who are accustomed to traveling Japan, Europe, and the US. Those sets of producers/coordinators will report to Sakamoto (DM)/Takahashi (GM) in Japan.
Tanabe not working directly with Retro on this next project doesn't mean it is because of this dramatic work that Tamaki may be fabricating. Nintendo has over a dozen US producers that switch between projects. Sakamoto is their boss now. Then Takahashi is Sakamoto's boss.
I will also make this point of reference over Tamaki. I'm friends with a few development personnel in Japanese and US based offices with direct relation or affiliation to Nintendo. I don't badger them about secrets, like ever. But when our conversations do steer towards Nintendo, it's clear to see how the company protects itself, and how the employees respect the company. Unless this dude is friends with a Pres. or Vice President, there is no single source that can provide such a range of rumors or insider news. Maybe he has befriended 20 developers at Nintendo, and they are all willing to talk. I don't know, but I think he is just a suspicious dude who seems to really enjoy the limelight.