It means you can for example no longer do things like get multiple disjoint references into the same buffer for parallel reads/writes of independent chunks.

Or well you can, using unsafe, Arc and Mutex - but at that point the safety guarantees aren’t much better than what I get in well designed C++.

Don’t get me wrong, I still much prefer Rust, but I wish async and references worked together better.

Source: I recently wrote a high-throughput RPC library in Rust (saturating > 100 Gbit NICs)