FYI there's a second translation on Mangadex. That one uses "Raising Heart". I haven't looked closely for other differences.
For any keen-eyed readers: the original Japanese used both 'Zed' and 'Zeo', that's not a translator error.
That feels like an alternate universe from the main series. At least there's Nanoha and hopefully, Fate won't be long to join, but yeah, that first chapter feels kinda out of place, somehow. Very little exposition as to what's going on and why a 13yo Nanoha is actually working for some military force.
We are forgettin that she is a 13 year old working!
Nanoha has been working off and on for the Bureau since she was 9, in the main series. 'Contractor' through A's I guess, but StrikerS had that backstory of her working too hard by Vita's side and getting crippled by a Gadget Drone... at age 12. How this was to be balanced with her also going to school in Japan was never expanded on, because let's face it, the franchise tends to be very bad at details like that.
So in itself, I'm not sure there's anything in this chapter that makes it obvious we're in the Reflection timeline. What bugged me was all this "United Nations" stuff. But I think the TSAB personnel are co-operating with the UN of this particular planet, and thus labeled with its authority. Like some years before making RF6, she'd made this "Exceeds" group locally. But like, was the Bureau even mentioned in this chapter?