I think it has more to do with the fact that your iDeco account is not managed directly by Rakuten, but by a third party (you can see how they try to embed portions of said third-party's website into their interface). Since this is Japan, the backend is probably from the early 90s, hence the long lag between the time your money leaves your account and the time it is actually reflected.
Rakuten iDeCo - where did my cash go??
Re: Rakuten iDeCo - where did my cash go??
Re: Rakuten iDeCo - where did my cash go??
The incredibly slow timing is one of the biggest drawbacks to the current iDeco system.
It shouldn't take weeks for each and every step.
It shouldn't take weeks for each and every step.