I did a quick search for this Aquador thing.

In concert with this device, is the pool not drained below the skimmer opening? That would be the idea right? Rather then drain the level of water below the skimmer opening so they can be "blown out", install this Aquador, leave pool water at functioning level, and blow skimmer out.

Correct?

Or is both done, aquador installed and pool lowered below skimmer opening?

In either case:

It's very hard, nary impossible to prevent water from getting into a skimmer body, regardless of the closing method. That's what the "gizmo" is for. If water gets into the skimmer body (the holding area, not the pipes leading to it), and freezes, that is the major concern. The "gizmo" in this circumstance would collapse as the water froze, rather then have that frozen water expand and push out on the skimmer body. A gizmo isn't long to the very top of your deck because they were designed assuming there was no aquador on the skimmer opening. Thus, water rising any higher then the gizmo is effective, would drain into the lowered pool.

My guess would be with this device on:

If very quickly (relative to rain fall and such), the water has risen to exactly the same height as the pool (if the pool wasn't lowered), I'd suspect the aquador has failed. What are the chances of rain fall filling the skimmer to that same height? If the aquador hasn't failed it would be a huge coincidence they were at the same level.

If there's only "some" water in the skimmer (again with the aquador on), I would suspect just water coming from other sources. Rain, condensation, law sprinkles maybe. Unless you actually seal the skimmer deck lid, water can and will get in there, how much and how often depends on the elements.

If it's the same level of the pool water and that water is not at the height of the aquador (lowered below skimmer opening), again just coincidence because the two don't affect each other. Unlike if the water was outside the aquador, and if it failed it would seek that same level in the skimmer.

My thoughts are in a climate where freezing is a possibility I would never trust an item like that. Solid frozen waterthrough the throat and body of the skimmer at the operational water heights could be a disaster. No gizmo could stop what could be a potentially powerful force. I've seen them (pools) freeze over completely and survive, but not often.

Hope this helps, I'm not familiar with the product and haven't used it so a lot of this is speculation on my part. I'm assuming a lot.