Git 2.33 shipped the 'ort' merge strategy as an option and Git 2.34 (November 2021) made it the default, retiring 'recursive'. Ort is a from-scratch rewrite that does not touch the index or working tree while computing the merge, which makes it far faster on large trees and lets it be used for merges that never get checked out.
Two observable consequences. First, conflict and progress messages changed wording, so any script grepping merge output for strings like 'Auto-merging' or the old 'CONFLICT (content)' formatting needs rechecking. Second, ort fixes several long-standing recursive bugs around directory renames and add/add conflicts, so a merge that previously conflicted may now resolve, or resolve differently. To reproduce a historical result you can still pass '-s recursive' explicitly, though it is deprecated. Check which one ran with 'git merge -v' or by looking for the 'Merge made by the ...' line on a non-fast-forward merge.