Thank you for all the feedback you've given so far, sveakul.
That comment in green from the image in my previous post appears to be a note from the AZ lyrics website (in html format) to providers like this plugin.
There was a discussion on it here and I also think it shouldn't be officially associated with MusicBee and the plugin:https://getmusicbee.com/forum/index.php?topic=25406.msg181755#msg181755
Edit addressing the second point of sveakul's post:
To anybody else with a comment on this, I'd like to hear more opinions on whether other providers should be built into the plugin or not.
I personally happen to agree with redwing on this note (the reply linked on the third post of this thread).
Making them optional sounds more advantageous to both user and maintainer, than making them defaults.
I noticed hiccup had "(news)" added to his custom sources to avoid conflicting them with old, and possibly broken built-ins at the same time.
With the way things are at the moment, he wouldn't have to wait for me to make any fixes if any providers are broken.
He would simply fix them himself and also avoid the inconvenience of having to manage duplicates.