What I am describing would be something higher level, more like a comment on approach, or an observation that there is some high-level redundancy or opportunity for refactor. Something like "in an ideal world we would offload some of this to an external cache server instead of an in-memory store but this is better than hitting the DB on every request".
That kind of observation may come up in top-level comment on a code review, but it might also come up in a tech review long before a line of code has been written. It is about extending that attitude to all aspects of dev.