"The usual way I've heard this explained, which seems reasonable, is that steel and iron are porous, and what causes sticking is the contraction of those pores when heated. A smooth covering prevents that sticking, and polymerized cooking oil provides that."

Not blaming you, but this is just wrong and a fundamental misunderstanding of steel and iron.

Cast iron (and steel) does not have pores. It is not like wood. SAE 304 (stainless steel commonly used in cheap pans) does have micro-cracks in the surface. These can be removed through honing or surface polishing, and the substructure is weird. Let's put it aside for a second, and stick with cast iron, carbon steel, and other stainless because 304 is just super strange stuff at the microscopic level.

Cast iron simply has no pores at all, just surface roughness. The average surface roughness is not that high (125 microinches or better)

Here is a high magnification photo of cast iron with the different microstructures pointed out: https://www.researchgate.net/publication/325977459/figure/fi...

here's one colored a little nicer: https://www.struers.com/-/media/Struers-media-library/Knowle...

You can see there are no holes and no pores. There are just some different types of microstructures.

Here is normal stainless steel: https://www.researchgate.net/publication/327401795/figure/fi...

(the one on the right is after sandblasting :P)

Liquids theoretically fill the surface roughness of either but not like massively. You can see on the stainless there just isn't a lot to even fill.

For all of them the overall flatness changes when heated, and the surface roughness changes slightly, but that's it. Not a lot. it definitely does not expand pores, or change the surface roughness by a factor of 10, or any of this.

This is why cast iron is used to make precision laps - to surface things like lab grade surface plates to like 0.000005 inches and such: it stays flat once machined and surfaced, it has lots of thermal inertia, and doesn't get screwed up by things sticking to it once polished[1].

If your goal is to make it so nothing sticks, by adjusting the surface roughness, you could also just sand it outside with a respirator on to like 2000 grit or 4000 grit and never worry about it. This would cost you about 5 minutes of time, maybe 10, and you can do it by hand if you want (though it's like 1 minute with an ROS).

I can show you a non-seasoned, "polished once 8 years ago to 8000 grit" cast iron griddle that has 0 rust, and is quite non-stick.

Manufacturers would do this except now they get you to do it for them, because people won't buy it unless they can season it to "add flavor" and such.

The whole thing has become a silly cargo cult honestly. The number of people who now think that like cast iron and steel have pores is also way too high :)

Besides sanding, there are other ways to change surface roughness that don't involve burning cooking oil onto something that doesn't need it. They also last much longer.

Also note that depending on temperature that people season at, they can release really toxic stuff. 300C (572F) is totally achievable on most stoves, by people just leaving them on to season, and will generate some very toxic byproducts.

"Funnily enough, I have. I built a bookshelf that uses raw steel beams, and I seasoned it to protect it from rust. 3 years in, it's still rust free (amusingly, except for the inside of the pipes)."

Visibly, or did you check under the coating?
Most seasoning just hides rust. It's still rusted, and as it gets removed it's just taking the iron oxide with it so it looks like it's not.

[1] Here's a fun side video of someone making precision laps out of cast iron using nothing but the 3 plate method, timecoded to when he puts the optical flat on it:
https://www.youtube.com/watch?v=Whyw5v7L70c&t=810s

The lines are straight because this cast iron is flat and not rough to at 1/10th or 1/20th the wavelength of light used here, which translates into an average roughness below 25-50nanometers.

You do not need to go this far to get a non-stick pan out of cast iron :)