That's an older version, but shouldn't matter.
--max-read-ahead SizeSuffix The number of bytes that can be prefetched for sequential reads (not supported on Windows) (default 128Ki)
Rclone and linux readahead - Feature - rclone forum
Update MAX_KERNEL_WRITE · Issue #309 · hanwen/go-fuse (github.com)
Some older info here too:
POC: thoughts into code for readaead by sjpotter · Pull Request #3926 · rclone/rclone (github.com)