But many developers probably use Safari Developer Mode to work on their projects, and this will help them.
Yes, but those developers don't get their recommendations from Consumer Reports. That magazine's audience would never have encountered that bug.
Obligatory car analogy: say they're testing a Ford Focus. They disable its antilock brakes so that a professional driver can get its best-case dry pavement stopping distance. Along the way, the find an OBD-II bug that causes the brakes to take twice as long to stop the car. They report the bad results instead of the normal, expected values. Yes, their test was correct! It found a bug that needs to be fixed. However, the only people who would ever see that bug are the exact ones who'd notice something was wrong and be able to troubleshoot it. You and I aren't ever going to disable our antilock brakes, even if a test engineer might.
I think that's kind of what happened here. Again, yes, they legit found a bug. My problem with it is that they reported the buggy results instead of the actual ones that a normal non-developer would see. A developer would notice their battery draining in a fourth the expected time and that it only happened when they were debugging in Safari, so they probably wouldn't even be significantly affected by the bug.