https://github.com/bitcoin/bitcoin/blob/d72758c3f6c34cd835f5de3efc230964f3b1ea56/src/torcontrol.cpp#L539

If a user is running Tor proxy outside localhost (perhaps on other host inside LAN or in containerised environment) , the automatic creation of onion services ends up creating an onion service listening to hardcored 127.0.0.1 address on the Tor proxy's host instead of the private address of the bitcoind – effectively running an empty onion service listening the Tor proxy's localhost.
proxyType addrProxy = proxyType(proxyAddr, proxyRandomize);
        if (!addrProxy.IsValid())
            return InitError(strprintf(_("Invalid -proxy address or hostname: '%s'"), proxyArg));
        SetProxy(NET_IPV4, addrProxy);
        SetProxy(NET_IPV6, addrProxy);
        SetProxy(NET_ONION, addrProxy);
        SetNameProxy(addrProxy);
        SetReachable(NET_ONION, true); 
    }
    
    
    
    std::string onionArg = args.GetArg("-onion", "");
    if (onionArg != "") {
        if (onionArg == "0") { 
            SetReachable(NET_ONION, false);
        } else {
            CService onionProxy;
            if (!Lookup(onionArg, onionProxy, 9050, fNameLookup)) {
                return InitError(strprintf(_("Invalid -onion address or hostname: '%s'"), onionArg));
            }
            proxyType addrOnion = proxyType(onionProxy, proxyRandomize);
            if (!addrOnion.IsValid())
                return InitError(strprintf(_("Invalid -onion address or hostname: '%s'"), onionArg));
            SetProxy(NET_ONION, addrOnion);
            SetReachable(NET_ONION, true);
        }
    }
    
    fListen = args.GetBoolArg("-listen", DEFAULT_LISTEN);