Many terms and frameworks evolve beyond their original intent, so I'm not too worried that this has evolved, too.

I've always found it is easier to understand servant leadership as the opposite end of the spectrum from autocratic leadership: Is the leader primarily concerned about growing their own power/success, or growing the power/success of those who work for them?

There is a lot of middle ground between those two extremes, but without that contrast in mind, you can easily lose track of what the terms mean. The article does a decent job of trying to find a healthier middle ground, IMO.