It is impossible to interpret this number (271) without looking into details. People certainly found plenty of memory safety and others bugs in Rust projects in the past, so I do not understand you claim that there too few to find any.
Curl reported 40% and more recently it dropped to about 20% of issues caused by their use of C. And this even with the requirement to stick to old C89. OpenBSD reported 30%. I assume the 70% either have to do with C++ or - more likely - there is a huge selection bias.