I completely disagree with this statement. If a Rust developer takes longer to code some feature this time will eventually be saved fixing memory bugs later on. And don't forget the immaterial cost of losing customer confidence if the product crashes or glitches because of memory instability.
And then I'm even glossing over the enormous benefit of Rust when writing correct multi-threaded code, which is almost always a minefield in C/C++. Code that looks and seems to work OK might in production suddenly crash after a year or so. A complete nightmare!
Memory safety is ALWAYS a good thing to have.