Not exactly. G+ was contemporary with / the spearhead for that initiative, but the desire to reify login was something Google was planning to do for awhile; they just used G+ as the focus project around which to pin the initiative. Nobody at Google was really thrilled with having three (four? five?) credential stacks, all with their own bespoke tooling, concept of what an "account" was, security stories, and administrative needs.

(... the one thing that came out of G+ that has stuck around is infrastructure improvements. A lot of the stuff the G+ team wrote to support Google+ behind-the-scenes is still used at Google for other projects now).