Possibly, But Not Necessarily...
There are a few theories out there that could explain the BIG plot twist at the end of the movie that may pertain to THESE minor plot twists, because of whom the source of information is (Grindelwald), may not validate the information given.
Theories about BIG plot twist:
Percival conceived a child with another women while in Azkaban.
The character in question could be a cousin rather than a brother.
Grindelwald used dark magic to to play a trick. (Thus Grindelwald is an unreliable narrator.)
In Support of #3 (Different Perspective Than Previous Answer)
There are some callbacks in this film to The Goblet of Fire,
which is also about dark magic creating a once thought-to-be
impossible situation. (AKA: Harry's name is put into the goblet
through dark magic, so the Phoenix visiting "So and So" could also be
some kind of dark magic trick/illusion. It's also a bigger
introduction to love triangles that begin to threaten "the team")
Note: Cho Chang is Harry's love interest in The Goblet of Fire/Order of the Phoenix (film version). Although the character is suppose to be either of British Asian or Irish Asian heritage, actress Katie Leung is Scottish born and of Hong Konger decent and her Scottish accent is clearly heard in the films. I brought this up because it bridges together thematic aesthetic and more through lines between The Crimes of Grindelwald & Goblet of Fire with love triangles & tragic death, imagery in lake with Scottish Kelpies (Loch Ness Monster), and Asian culture/foklore with the Chinese Zouwu.
There is also this "French Connection"...
However, I feel that most references tend to callback Order of the Phoenix, especially with such a similar narrative of "a call to arms", but that film relies a great deal IMO on the events featured at the end of The Goblet of Fire, such as the return of Voldermort and the death of Sedric Diggoray, even tying Harry being able to Thestrials due to that event.
I feel that, although more adventurous, Fantastic Beasts and Where to Find Them is in similitude with the first two Harry Potter films being more kid-friendly and lighter on the darker elements. The Crimes of Grindelwald is more like a mash-up between Prisoner of Azkaban, Goblet of Fire, and Order of the Pheonix.
I think this all points to an idea that viewers shouldn't trust Grindelwald and the information he passes onto the audience.
About The Blood Pact
J.K. Rowling has this habit of introducing objects or other things of interest that doesn't get fleshed out until much later. In Example the Triwizard Trophy is introduced as the first unexplained portkey at the end of The Goblet of Fire. It may then be possible there is some catch 22 with a blood pact that we don't understand.
Some *speculation I have come across is that, it only makes sense that the blood pact happened before the duel, but perhaps Albus was only blocking spells between Aberforth and Grindelwald whom may have already been actively engaged, as opposed to Albus being the one offensively dueling another. There could be a catch 22 about dueling.
A simpler explanation that others believe that maybe he just tried dueling anyways and the spell was rebounded due to the blood pact and accidentally killed Ariana.
At any rate there could surely be reasons, as opposed to Rowling directly retconning