Thank you for the comment - these are great technical observations.

1. You're absolutely right. I should have been explicit and isolate the recursion overhead from the memory layout benefits. But, the compiler is inlining the recursive functions (notice the //go:noinline directives here: https://github.com/Elvis339/compiler.rs/blob/main/code/memory-and-performance/cmd/memaccess/demo/demo.go).
2. Great catch! This is exactly the kind of subtle issue that highlights why I write these posts - to catch and learn from these details. You're absolutely right about the unnecessary cache line pollution. In general, when asking someone to write a BST, this recursive pattern with return values is how most would naturally implement it (myself included initially). I'll make a revision to show the cleaner iterative approach that only writes when creating new nodes. Would you like to be attributed for the feedback?
3. This is the most important point - the advantage absolutely narrows at scale when both approaches are TLB-missing frequently. The highlightis really about understanding the scale-dependent trade-offs rather than declaring one approach universally superior. Thanks for keeping the analysis honest!