I don't know that we at the network/protocol inspection level have a way of distinguishing specific SFTP applications - they're likely all the same at the protocol level. This might be something that's more suitable to do at the application level, but please do work with your local SE on an RFE.
File types can be blocked with AV or TE blade, which are both supported via SSH DPI, so that you can do today. With AV you can configure the Threat Prevention profile under AV > File Types an action per file type for supported files (bypass, inspect, block) or in TE you can add a list of prohibited file types.
TE: https://support.checkpoint.com/results/sk/sk123140