does a pack cover make sense for dyneema packs?

Hi,

There's a chance of rain this weekend in the Sierras, and I'm wondering if I should take my pack cover in addition to using a liner in my Lowe Alpine Zepton 50. They claim the pack is made from dyneema. I'm fairly confident that the liner will keep my stuff dry. It's excessive weight gain from water absorption that I'd like to avoid. I've seen some old posts where they talk about significant weight gain, but I think the pack fabrics were different.

thanks,

rhz