There's a number of nodes that present two options, but one leads to a bad ending and one leads to a blocked ending, the reason being that you need to uncover a new special ability that can only be found by travelling through time. These blocked endings become unblocked after getting the special ability, so the original blocked ending becomes inaccessible after that point.
The question is, do I need to visit the blocked ending first before getting the special ability to unblock it for 100% completion, or, if I know I'm coming to a blocked ending, can I go get the special ability without viewing the blocked ending, and not miss out on completion rating? I'm actually playing through without having beaten it or using a FAQ, since it seems that it's only a matter of time (pun intended) before one reaches 100% completion... or is it?
I plan on eventually at least trying to see all the blocked endings, but I'm a bit of a completionist, so I'd rather try and get 100% at least once, so I could save some time if I see an obvious special ability ahead of time. Since I've already played about half-way through previously (I traded Radiant History for Perfect Chronology), I know a bit about the story, so I can save some time, if it won't harm my completion percentage.