As part of Apple's flurry of Mac announcements earlier this week, the company announced the new M5 Pro and M5 Max processors. And those chips are shaking up the way that Apple designs and talks about its processor cores: What would have been called "performance" CPU cores are now "super" cores. "Efficiency" cores are still called efficiency cores. And there's a new, third type of CPU core in between that is labeled a "performance" core.
Apple said earlier this week that the "super" name change would retroactively apply to the regular-old Apple M5's performance cores, too. And the macOS Tahoe 26.3.1 update released yesterday officially made the name change, changing the labeling in both the System Information app and the Activity Monitor.
This "upgrade" should only apply to the M5 MacBook Pro, the sole M5-family Mac released before the name change was announced. It should go without saying that this is just a name change; you shouldn't actually expect different behavior or performance from your Mac after installing the update. The new MacBook Airs and Pros with M5, M5 Pro, and M5 Max chips will likely already be using the new names out of the box.