I never had to do that and it always worked.
Discussion
If you don’t do that, then ln.tips LNURL response won’t include the NIP-57 required fields of `allowsNostr` and `nostrPubkey`. So, without adding your nostr pubkey to ln.tips bot, you can still receive sats over lightning network, but they are not NIP-57 Zaps. This means they won’t show up in your nostr client.