The _recording_firstreleasedate is not the date of when the music was recorded. It is the earliest date this specific recording was released (according to the info available in MusicBrainz). If you look at the recording page you will see on the right sidebar:
First release year: 2006
That’s because this particular recording is listed on two releases, one from 2006 and one from 2014.
As this was recorded in 1969 we can likely assume this specific recording was also released somehow earlier, but this info is not on MB (either the release is not there, or the recordings are not merged).
If you are looking for the date of recording have a look at the plugin from the following thread: