The article mentions:

The Israeli military took foreign journalists into southern Lebanon on Sunday and showed them a Hezbollah tunnel shaft that was less than 200 metres away (650 feet) from a UNIFIL position, as well as weapon stashes that the troops found. Brigadier General Yiftach Norkin said the tunnels had been built a few years ago. “We are actually standing in a military base of Hezbollah very close to the to the U.N.,” Norkin said, pointing to the shaft’s trapdoor in an area covered by undergrowth and overlooked by a U.N. observation post.

You might or might not believe their claims or evidence here, but the reasoning seems to be that Hezbollah is utilising UNIFIL as shield