Proxy working in CURL but not in WinSCP

Dear forum members,
I am migrating my communication scripts from curl to WinSCP, and there is one connection that does not work.
By examination of the logs of both tools, I see that CURL is using the GET method to the http proxy, while WinSCP is launching CONNECT.
Maybe this is the reason? In that case, how can I make WinSCP use the GET method?
Thanks in advance for your help

Find below the log of the two operations:
------------------- curl
D:\Apps\curl>D:\Apps\curl\curl.7.40\bin\curl ftp://ftp.partner.com/ --list-only --user ftpuser:ftppass --proxy myproxy.mydomain.com:8080 --verbose
* Trying 10.33.254.120...
* Connected to myproxy.mydomain.com (10.33.254.120) port 8080 (#0)
* Server auth using Basic with user 'ftpuser'
> GET ftp://ftpuser:ftppass@ftp.partner.com/ HTTP/1.1
> Authorization: Basic B64Enconded
> User-Agent: curl/7.40.0
> Host: ftp.partner.com:21
> Accept: */*
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 200 OK
< Content-Type: text/html
< Transfer-Encoding: chunked
< Proxy-Connection: Keep-Alive
< Connection: Keep-Alive
< Date: Fri, 01 Jun 2018 14:15:11 GMT
<

------------------- WinSCP
. 2018-06-01 16:16:08.047 --------------------------------------------------------------------------
. 2018-06-01 16:16:08.047 WinSCP Version 5.13 (Build 8172) (OS 6.3.9600 - Windows Server 2012 R2 Standard)
. 2018-06-01 16:16:08.047 Configuration: D:\Apps\WinSCP\5.13\WinSCP.ini
. 2018-06-01 16:16:08.047 Log level: Normal
. 2018-06-01 16:16:08.047 Local account: AD\user
. 2018-06-01 16:16:08.047 Working directory: D:\Apps\WinSCP\5.13
. 2018-06-01 16:16:08.047 Process ID: 20900
. 2018-06-01 16:16:08.047 Command-line: "D:\Apps\WinSCP\5.13\WinSCP.exe"
. 2018-06-01 16:16:08.047 Time zone: Current: GMT+2, Standard: GMT+1 (Romance Standard Time), DST: GMT+2 (Romance Daylight Time), DST Start: 25/03/2018, DST End: 28/10/2018
. 2018-06-01 16:16:08.047 Login time: viernes, 1 de junio de 2018 16:16:08
. 2018-06-01 16:16:08.047 --------------------------------------------------------------------------
. 2018-06-01 16:16:08.047 Session name: SIVO-ES (proxy-metier) (Modified site)
. 2018-06-01 16:16:08.047 Host name: ftp.partner.com (Port: 21)
. 2018-06-01 16:16:08.047 User name: ftpuser (Password: Yes, Key file: No, Passphrase: No)
. 2018-06-01 16:16:08.047 Transfer Protocol: FTP
. 2018-06-01 16:16:08.047 Ping type: Dummy, Ping interval: 30 sec; Timeout: 15 sec
. 2018-06-01 16:16:08.047 Disable Nagle: No
. 2018-06-01 16:16:08.047 Proxy: HTTP
. 2018-06-01 16:16:08.047 HostName: myproxy.mydomain.com (Port: 8080); Username: ; Passwd: No
. 2018-06-01 16:16:08.047 Send buffer: 262144
. 2018-06-01 16:16:08.047 UTF: Auto
. 2018-06-01 16:16:08.047 FTPS: None [Client certificate: No]
. 2018-06-01 16:16:08.047 FTP: Passive: Yes [Force IP: Auto]; MLSD: Auto [List all: Auto]; HOST: Auto
. 2018-06-01 16:16:08.047 Local directory: default, Remote directory: home, Update: Yes, Cache: Yes
. 2018-06-01 16:16:08.047 Cache directory changes: Yes, Permanent: Yes
. 2018-06-01 16:16:08.047 Recycle bin: Delete to: No, Overwritten to: No, Bin path:
. 2018-06-01 16:16:08.047 Timezone offset: 0h 0m
. 2018-06-01 16:16:08.047 --------------------------------------------------------------------------
. 2018-06-01 16:16:08.063 Connecting to ftp.partner.com ...
. 2018-06-01 16:16:08.078 HTTP proxy command: CONNECT ftp.partner.com:21 HTTP/1.1

. 2018-06-01 16:16:08.078 Host: ftp.partner.com:21

. 2018-06-01 16:16:08.078

. 2018-06-01 16:16:08.109 Connection with proxy established, performing handshake...
. 2018-06-01 16:16:23.094 Timeout detected. (control connection)
. 2018-06-01 16:16:23.094 Connection failed.
* 2018-06-01 16:16:23.110 (EFatal) Connection failed.
* 2018-06-01 16:16:23.110 Timeout detected. (control connection)
* 2018-06-01 16:16:23.110 Connection failed.

WinSCP does not support GET. Actually what curl does, does not seem like FTP session at all.