There is a big difference between the guidance in the GHI document link and the softwareengineering link.
The softwareengineering link shows stack variables, and the GHI docs use the ‘new’ operator. The two behave very differently. The guidance to initialize and reuse a single allocation using ‘new’ is very important for avoiding needless memory churn on the heap. However, the softwareengineering example is dealing with stack (not heap) allocations, so the only cost here is the execution (time) cost of moving the stack pointer repeatedly rather than once.
Both are good guidance, but the minimization of ‘new’ in loops is an essential best practice for TinyCLR programs (and arguably all managed-code programs).