If you don’t have style rules baked into the PR process, you should. Tabs vs. spaces is a team decision and needs to be matched by everyone to reduce code churn. It’s correct to reject a PR if it violates the team style guide (although it should be automated and have tooling locally to enforce it as well.)

the only thing that matters is making money fast. everything else DOES NOT MATTER, and ESPECIALLY not the invisible characters between the words.