Most people will not see it possible or convenient for themselves to keep their seed phrase far from themselves
It's not convenient, but if the alternative is losing everything, then it is preferable. It doesn't have to be the only copy of your seed phrase - obviously you can keep one close by which is convenient to access should you need to - but any back up which is safe from catastrophes in your local area will by necessity be inconvenient for you to access.
If a 1000 tonne building falls on your seed no thick metal is going to prevent it from getting damaged it would be damaged beyond repair.
Good quality stainless steel of a reasonable thickness would survive just fine, especially something 2" thick as you suggest.
If a 1000 ton building collapses, then that full 1000 tonnes will be spread out over the entire area that the building collapses on to, which will be the footprint of the building plus more, since the rubble will fall in all directions. An average steel plate is maybe around 10 square inches, a tiny fraction of the total footprint. And as I said above, Lopp's stress testing shows that such devices can easily withstand 20 tons of pressure. To have 20 tons of pressure on 10 square inches, you would need all 1000 tons of the building to collapse on to an area less than 2 foot by 2 foot, which is obviously crazy.