The problem of the CPU reordering things only exists on architectures like Alpha. However, there's still the problem of the compiler reordering things (which exists on every architecture), and memory_order_consume was intended to solve both. As you can see from the original rationale document from 2010, this RCU use-case was one of the main motivations:

https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1525.htm