nMap scan ssl cipher list fail if argument -sV added - c

Question

To All,
I am writing a service running HTTPS protocol that accept secure connection using Openssl.
After that, I tested SSL connection using nmap with the following command:
nmap --script ssl-enum-ciphers -p 443 192.168.2.1
Nmap scan report for 192.168.2.1
Host is up (0.0029s latency).
PORT STATE SERVICE
443/tcp open https
| ssl-enum-ciphers:
| TLSv1.2:
| ciphers:
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 (secp256k1) - A
| TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (secp256k1) - A
| compressors:
| NULL
| cipher preference: client
|_ least strength: A
However, if the the argument -sV is added, then it displays following
nmap --script ssl-enum-ciphers -sV -p 443 192.168.2.1
Starting Nmap 7.01 ( https://nmap.org ) at 2021-05-25 09:15 CST
Nmap scan report for 192.168.2.1
Host is up (0.0030s latency).
PORT STATE SERVICE VERSION
443/tcp open ssl/https?
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 12.79 seconds
the -sV is used to probe service/version info, I am wondering is it because I am using ECHDE only?
Anyway, here's how I setup my SSL connection (Remove error checking for easy reading).
SSL_library_init();
SSL_load_error_strings();
CTX = SSL_CTX_new(TLSv1_2_server_method());
SL_CTX_set_cipher_list(ctx, "ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384");
SSL_CTX_ctrl((CTX),SSL_CTRL_SET_ECDH_AUTO,1,NULL);
SSL_CTX_use_certificate_file(CTX, pem, SSL_FILETYPE_PEM);
SSL_CTX_use_PrivateKey_file(CTX, pem, SSL_FILETYPE_PEM);
SSL_CTX_use_certificate_chain_file(CTX, chain);
I am suspecting the ciphers ECDHE, because if I use Cipher list "AES128-SHA256:AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384", everything seems to work fine.
Any help is appreciated, thanks.