So regardless if anything, should you store them in a hard wallet?
If yes, and the world changes in terms of blockchains, splits etc isnt there a chance your offline keys can be worthless or problematic to cash or convert in the future since you stored them one way back in the day and now things work differently, code is different etc.
Its always recommended to own the private keys. If you store the Bitcoin today to your wallet, there is no way the private keys going to be incompatible with Bitcoin in the future.
The problem if you dont own the private keys (like on Coinbase) is you just might get your Bitcoin, but if you own the private keys you have potentional access to both Bitcoin and USAF BIP148 coins (or any future minority split coins, or any alt coins based on Bitcoin ledger - like Clams in the past).