My deductions are that these were installed to accomplish both. Similar to what auto manufacturers do in their products.
The better thing to add would be rubber drain tubes, just like auto companies due. These allow drainage & breathing yet prevents water from splashing up into the holes.
What I have discovered after obtaining & rebuilding my '76 Sovereign
is that AIRSTREAM fail to seal the 'underbite' lap where the bellypan wraps over (instead of under) the sidewall skins. Big mistake!!
Since this joint was not sealed it was a HUGE water inlet with no place to go except linger it the perimeters of our trailers. Being soaked up by what little insulation was there and causing a slow death -by corrosion- to the frame members, mostly the outriggers. Was this "Planned Obsolencence?" ARRGGH!! Shame on AIRSTREAM!
Think about this, water in with no way out? Hmm, would we build a house this way?
Anyway, I have replace several outriggers, oddly most were on the roadside, replaced the entire floor with R13 fiberglass & new perimeter belly wraps and will be sealing this critical area at the belt line (with VULKEM) & installing automotive type body drain tubes thrughout as well.