This thread sparked a question in my head. Imagine that you are in a situation where you need to dispose of you wallet seed backup, but it is etched on a steel plate - how would you do it? The easiest answer is likely acid, but not everyone has access to it, and depending on the steel plate, it might be even highly resistant to corrosion. Another option is to damage it mechanically - in many of these steel plate products you are supposed to etch the words, so it should be possible to erase them or render unrecognizable. But it's likely hard to do thoroughly and traces of the words could remain.
Any more ideas?
Steel Plates were created in order to prevent seed phrases from any kind of damage, so what you are asking for is counter-productive, you shouldn't buy steel plates if you plan to destroy them ever.
It's not totally useless because it contains your transaction history and you might want it not fall into other's hands. Also there could be situations where it's not an option - you want to destroy just a backup, not the wallet. Imagine you have two backups, one at your current location and another at a remote and safe location. Let's say you are moving from your current location to some new one where you wouldn't keep your steel backup with you because the new place is not safe enough. So you'd want to destroy the backup at your current location, while still relying on the backup at your other safe location.
Seriously, that's not totally useless, that's the best solution in this case. If you don't want to get tracked, then use a mixer or exchange bitcoins for altcoins, there are many ways to minimize tracking and improve privacy or use paper wallet and it will be over.
Long story short, use metal seeds if you don't plan to destroy them or if you think you'll have a moment when it will be necessary to destroy seeds, use a paper wallet or any different method with the possibility of destruction.