I have a hard time believing that anyone who holds/controls large sums of bitcoin are going to keep it in places that can be identified as being owned by one person or entity (unless they are a public company or a government that has to make those kinds of disclosures).
If I were to hold any appreciable amount of Bitcoin (I do not, of course) I would set it up so that it was stored in a multisig cold storage setup (optionally with hardware wallets separately geo-located). But I would also backup the private keys for each address with <1BTC. No addresses would have more than, I dunno, 0.7BTC and all slightly different. But there would be a spreadsheet, created on an airgapped laptop, that was GPG encrypted that held those individual keys... You know... In case. I would have created detailed instructions on how to access all these Bitcoin (1. With hardware wallets, 2. With Seed Phrases and passwords 3. With individual private keys in the worst case scenario), and trained my wife, and eldest child on the procedure.
But I do not have that sort of Bitcoin stash, so I just hold what I have on Coinbase.
Plus if i DID have that sort of stash?? All those details up there? Different than what I (would) have really done.
Or not?
Nevermind...
I just put them on different phones and write down the seed by hand on a piece of paper, I think you are overdoing it.