WinSCP Transfer to Temporary Filename Not Working

In WinSCP, I found that when uploading file to the server, the file doesn't have a temporary filename extension ".filepart".

Enable temporary filename for all files in "Preferences -> Transfer -> Endurance" still does not work.

First I think it's a bug for WinSCP 6.3.3, I attempted to use old version 5.21 but it also has the same issue.

After investigation, the reason is that this feature is only available for SFTP protocol, while I use SCP protocol to connect the server.

The solution is to modify the "File protocol" to SFTP.

Reference:

Locking files while uploading / Upload to temporary file name

Transfer was successfully finished, but temporary transfer file … could not be renamed to target file name …

SCP vs SFTP - 5 Key Comparisons | JSCAPE Managed File Transfer