I particularly like this idea cause it's something anyone can install themselves using a couple of work tools. I immediately write off any idea to secure financial assets that requires getting a third party to install cause that opens up more possibilities of getting involved in a $5 wrench attack.
There are many other secured ways to keep your stuffs private. I'll also be wary of using an electronically activated system, in this case if it goes wrong one can always break up the tiles
Whereas, though this may look like a best approach to hiding your Bitcoin wallet seed phrase or other valuables from third party, it won't still be enough security measure if that seed phrase is not written on materials that are fire and water proof.
Natural disasters like floods of fires will make it almost impossible to recover your wallet even with the seedphrase written on materials that are resistant. Better option will be to have your back up in multiple locations.
I think there should be a debate about carrying your seedphrase with you everywhere you go or keeping them in a safe at home, I think none is safe, it is a risk keeping your seed at home or carrying it with you, the only way to limit risk is knowing your country very well, we don't have natural disaster here so no need to prepare for any of that, but fire can break out, before you even remember that you keep your hardware wallet in a safe it can be too late already, but for someone who takes the key everywhere they go, all they have to do is run for their lives, and their money follows.
Anyways, I will just say it is better to be ready for anything, having your keys safe in more than one place is not completely safe either, it is a risk we all gotta take anyway, even been alive as a human is risky too.