Does nping connect without a full handshake?

[CoDDoC via dev <dev () nmap org>]

Hello to all!
 
I nping my test server to check iptables rules.
My command is (from Windows host):
nping --tcp --dest-ip x.x.x.x --dest-port xxxx --flags syn --count 1
 
I see only sent packet without answer:
 
Starting Nping 0.7.91 ( https://nmap.org/nping ) at 2021-07-20 13:45 RTZ 2 (ceia)
SENT (0.0470s) TCP y.y.y.y:yyyy > x.x.x.x:xxxx S ttl=64 id=30211 iplen=40  seq=2267374717 win=1480
Max rtt: N/A | Min rtt: N/A | Avg rtt: N/A
Raw packets sent: 1 (54B) | Rcvd: 0 (0B) | Lost: 1 (100.00%)
Nping done: 1 IP address pinged in 1.05 seconds

Then, i modify command like this:
nping --tcp-connect --dest-ip x.x.x.x --dest-port xxxx --flags syn --count 1
 
Now, I see tcp handshake:
 
Starting Nping 0.7.91 ( https://nmap.org/nping ) at 2021-07-20 14:13 RTZ 2 (ceia)
SENT (0.0300s) Starting TCP Handshake > x.x.x.x:xxxx
RCVD (0.0300s) Handshake with x.x.x.x:xxxx completed
Max rtt: 15.000ms | Min rtt: 15.000ms | Avg rtt: 15.000ms
TCP connection attempts: 1 | Successful connections: 1 | Failed: 0 (0.00%)
Nping done: 1 IP address pinged in 0.04 seconds
 
After this I repeated previous command:
nping --tcp --dest-ip x.x.x.x --dest-port xxxx --flags syn --count 1
 
And now I see packets in both directions:
 
Starting Nping 0.7.91 ( https://nmap.org/nping ) at 2021-07-20 14:20 RTZ 2 (ceia)
SENT (0.0560s) TCP y.y.y.y:yyyy > x.x.x.x:xxxx S ttl=64 id=21871 iplen=40  seq=2624730844 win=1480
RCVD (0.0560s) TCP x.x.x.x:xxxx > y.y.y.y:yyyy SA ttl=64 id=0 iplen=44  seq=176100673 win=14600 <mss 1460>
Max rtt: 0.000ms | Min rtt: 0.000ms | Avg rtt: 0.000ms
Raw packets sent: 1 (54B) | Rcvd: 1 (46B) | Lost: 0 (0.00%)
Nping done: 1 IP address pinged in 0.15 seconds
 
So, a question is: does nping connect without a tcp handshake? Or it's necessary to establish full handshake first?
 
Thanks in advance
 
--

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