There're two possible locations for xdb_wallet.
The root entry of xdb_wallet is $ORACLE_BASE for single-instance databases.
The root entry of xdb_wallet is $ORACLE_HOME for RAC databases.
That's the difference.
Putting wallets including Transparent Data Encryption (TDE) keys in $ORACLE_HOME has some advantages, one of which is that, when we backup Oracle home, wallets are also included.