I don't think the article is clear about it, contrary to your comment and a sibling. I read it as:

1. The soldiers were displaying IDF military flags at a music festival. This was not allowed by festival organizers and obviously pissed some people off.

2. These soldiers were then taken in for questioning.

It's not clear to me that these 2 were some of the specific 1,000 soldiers from that Hind Rajab Foundation report - that sounded like an associated piece of information given in the article.