I don't use the full SDK, so maybe that's the difference. I use the minimal ADB and fastboot from Google as linked by Android Police here: http://www.androidpolice.com/2017/0...ble-without-full-sdk-android-studio-download/.
It was last updated on March 13, but ADB hasn't changed since last December. That doesn't explain the huge version difference, unless that is the SDK version itself.
The link I posted is not for the SDK. It's only ADB and fastboot directly from Google, and up to date. Relatively new offering.