No, it is not “insecure.” It aligns with OWASP guidance: https://cheatsheetseries.owasp.org/cheatsheets/Forgot_Password_Cheat_Sheet.html

When would it be problematic? It would be problematic if they sent your actual password in cleartext as part of the “reset.” This would show that they can access your password in plain text within their database, which is the worst way of storing passwords on servers. (Dedicated password hashing algorithms exist to securely store passwords.) What they provided you is a one-time password.

I suggest waiting for the report of the official investigation.

what training scenario were they doing

As reported the days before (translated from German):

According to the Bundeswehr, the deployed forces are to train operations against threats behind a fictional front line, in what is referred to as the “rear area.” This includes scenarios involving drones, sabotage, or so-called “irregular forces,” meaning armed fighters not belonging to a state army. The assumption is that a NATO member state is attacked, and the alliance must respond to defend it.

Training will also focus on tasks such as working at crime scenes, directing traffic, locating weapon caches, combating illegal arms trade, and protecting critical infrastructure, for example, at the decommissioned Isar 2 nuclear power plant. Soldiers will also practice defending against enemy drones and deploying their own.

How do you do a training in public space without extensively informing the population beforehand?

Before, various German national, regional, and local media outlets reported extensively on this exercise. Commentators on BR complained that this seems like a routine exercise, questioning why it should be considered anything more than a local headline.

And such exercises require approval from other government authorities. It’s not saying, “Let’s just drive to the city and practice shooting.”

train with live bullets

How exactly does one train shooting at human targets (soldiers presenting the enemy or locals) with live ammunition?

This could mean that health and fitness data is being transferred to US companies. While this may not be a dealbreaker for many people, I appreciated having an alternative from the UK to the major providers in the US.