Ooops - I meant 1995 is when he renovated

That's not flooring, that appears to me to be more like the subfloor.

Not necessarily. We have a 1875 dog trot that has gaps where you can see outside. Airflow was part of the pre-hvac design in that case, high ceilings too.

Those boards were probably never meant to be exposed as floorboards, but would likely have had a linoleum or rugs or oilcloth for low maintenance.

There's no reason not to have them as finished floor now, however, if you can live with the dust-attracting gaps!

If they're pine, it's quite hard to get a paint to wear well, because even old pine is a bit soft and scuffs easily.

I think if I were you I would finish them with Rubio Monocoat, which now comes in a variety of stains, which you might find wears better than a paint. It's lovely stuff to work with, absolutely no VOCs, and you only need one coat, so although it's expensive there's no waste, you won't be choking and crying on toxic fumes, and you'll be done in a day. Takes a few days to cure completely.

I already shared this link once this evening, lol: http://www.monocoat.us/2C-Oil/

They're a lovely company to work with. Lots of informative videos on Youtube, and you can talk to them on the phone as well.

You could fill those gaps and not loose the look too if you want. I saw this one restoration project where they filled them with a 100% silicon. The filler look similar to the expansion joint filler used on concrete floors...it was colored. After filling them higher than the surface, they came back in after it cured and cut the excess off the top with a razor blade. It looked fantastic!