One of these [denied attacks] was the successful use of over twenty armed drones in late 2019 to attack Saudi oil production facilities. Iran attributed this to Shia rebels in Yemen that have substantial, but unofficial, Iran backing. This enables Iran to deny responsibility for the 2019 attack because that would have been an act of war and had some very real and very destructive repercussions for Iran. Instead Iran claimed that the attack was carried out by the Yemeni Shia rebels.
The Saudis were able to collect fragments of the several UAVs involved and reconstruct them. It was obvious that most of these UAVs did not have to range to travel from Yemen to northeast Saudi Arabia. The only other launch area was in nearby Iran.
So what if Iran denies they attacked Saudi Arabia?
Saudi Arabia knows Iran attacked Saudi Arabia. That 2019 attack was an act of war regardless of whether Iran admits they committed an act of war. Why wouldn't the Saudis just treat it as an Iranian act of war?
Not that we aren't guilty of this over Russia's invasion of Ukraine or even over Iran itself.
NOTE: Well, I screwed up the title as I intended it anyway, so why not edit it to make it more accurate?