Whilst Rusts memory safety rules no doubt help greatly to prevent memory related security issues. I would not over sell the point.
It is still trivially easy to reuse a byte buffer for multiple purposes. For example to receive data into and then send that data elsewhere.
One of the first bugs I made in Rust was just doing a read into a buffer and then a write from the buffer. Forgetting the read might not filled the entire buffer and writing the entire buffer rather than the length that was read. Thus potentially sending sensitive data to the wrong place.