I am unable to list unspent unconfirmed transactions for watch-only addresses. Once the transaction gets at least 1 confirmation it gets included in the returned result.
This is the command I am running (split into multiple lines for easier comments):
bitcoin-cli -rpcwallet=*** # redacted wallet name listunspent 0 # minconf 99999 # maxconf  # addresses - empty seems to mean all true # include_unsafe
Whether this output is considered safe to spend. Unconfirmed transactions from outside keys are considered unsafe and are not eligible for spending by fundrawtransaction and sendtoaddress.
This statement makes me think that this is an actual bug. It's worth noting that for addresses generated by wallet (not watchonly) unconfirmed transactions are showing just fine...