There are two issues which are not addressed in your article.
1. For some odd reason Google doesn't accept a gmail alias of the format "email@example.com" but insists on the root email.
2. The new versions 4.x Android app is the worst upgrade ever. Have a look on the FitBit forum and the Play Store reviews.
The official Google response has been to direct customers to help pages, tell them that there will be no app rollback to 3.x and to delete complaints that they do not like.