Loot currently function with a ‘legacy’ setting that kicks in when 11 levels above the content, and which forces the raid to drop a handful of items each boss.
There is no such thing as a ‘legacy power buff’ that triggers based on being some number of levels above an instance, though they did add a ‘legacy power buff’ for legacy instances the last time they did a stat / level squash - but that was at least 2-3 expansions ago and was done to keep relative player power in legacy instances similar to what existed prior to the stat / level squash.