Yes.

Well yes but since generations of climbers have been climbing and falling on wet ropes and climbing in humid areas without drying their ropes and they don´t break then it can´t be much of an issue anyway. To "dry" a rope which has been long-term stored in humid conditions would take ages since the moisture uptake is very much slower than most people realise.

A wet rope is significantly weaker than a dry rope due to the internal pressure effects.

Nylon isn't affected by water so humidity really isn't a problem long term.

Rubbish, nylon starts to effectively de-polymerise and weaken. This has been known since the 1930´s when removing all the water was the breakthrough in creating a usable form of nylon.

Rubbish, nylon starts to effectively de-polymerise and weaken.

A wet rope is significantly weaker than a dry rope due to the internal pressure effects.

Nylon isn't affected by water so humidity really isn't a problem long term.

The first part of your post is rubbish as the reduction in strength is nothing to do with internal pressure(whatever that means anyway).

[accident analysis]
... 12-inch circ. [~3.75" dia] 8-strand nylon 6.6 rope stretchers ...
The ropes were made up into grommets with soft eyes.
[think dogbone]
... would give a new dry strength of about 215 tonnes
and a wet strength of about 190 tonnes [88%].
...
Tests showed that the ropes would lose about 4.4%
of strength per day in this kind of towing service,
due to internal cyclic abrasion of wet nylon.

[Handbook of fibre rope technology]

Your climbing rope is changing size and strength on a daily basis depending on temperature and humidity which is why ropes have to be conditioned to a specific temperature and moisture content before testing.

If the rope is really soaked, and used (may be abused), it's significantly weaker that I would suggest to take care to try not to fall on it.
If it's iced, even worse.

And aren't dry ropes treated to keep out water and moisture?

Yes, but it actually wears off quite quickly, especially if the rope is used for rock climbing. Some manufacturers advertise that each strand is dry treated, and these may resist water absorption a bit better, but it still doesn't really keep the rope dry.

Dry treatments are meant to reduce the absorption of water to keep the weight of the wet rope down and to try to prevent it from freezing into unmanageable wire. It's not done for strength when wet or to achieve longer storage times.

Dry treatment for rock climbing ropes is an unnecessary extra expense imho.

not totally unnecessary. It keeps dirt off, too.

I just realized this advantage of a dry rope a few days ago, so strange to see it 'confirmed'. I bought my first ever non-dry rope last year, and despite very, very little use, it is now significantly dirtier than any previous rope I have owned.

TE

The dry coating put onto ropes is mostly a gimmick. It works great when the rope is brand new, but with minimal use even the best dry coatings will wear off very quickly.

In drop tests dry treated ropes consistently hold more falls than otherwise identical non-dry ropes. There is also evidence that they are more durable.