JSch uses multiple requests to pull files from / push files to a SFTP server. The number of bulk requests can be configured via ChannelSftp#setBulkRequests(int). The API documentation states that increasing this value may slightly improve file transfer speed at the cost of memory usage.
The configuration option should be made available in Camel.
I came across an issue with a specific SFTP server product. I tracked this issue down to the way bulk requests are sent to the SFTP server. To cut a long story short (details here) setting the number of bulk requests to 1 solves the problem, so it would be nice to have this option available via Camel.