They are not ruling out the tsunami possibility, just saying its very unlikely. Id agree. However, localized tsunamis caused by landslides have happened in Alaska. Luckily they were contained by the bays and coastal islands where they happened. The slippage of the Northwest American subduction zone has created tsunamis that did a lot of damage to Japan.
Las Palmas would be most likely if the volcano explosively erupted sideways (like St. Helens). Not a big chance but the likelihood isnt 0.
Yup. I read that some researchers suspecting a (earthquake) tsunami in the northwest in 1700 confirmed their suspicions by reading some Japanese history about a tsunami in 1700.
There are huge ancient underwater landslides around the Hawiian Islands.
Here:
Giant Landslides of the Hawaiian Islands