BTW, am I correct in assuming that "3xpl" hasn't been added to the list due to not having a rating up to this point, or is it something else? 
Regarding this explorer, as far as I see, Bitcoin_Arena said he can't rate it and since then nobody did it... If you look at 1miau's post (just next to the one you linked), he told Bitcoin_Arena to wait until someone would rate this explorer, in order to have some information about it but, since then, nobody did it... This is why it was not added to OP yet...
My coment back then:
There is this new Bitcoin block explorer it just got to know about today. It also supports other notable chains. It has a nice UI. However, I can't rate as I have just known it only today, maybe someone can help rate it
https://3xpl.com/bitcoin
Tor Link: http://3xplor3rzajysy4j5fi3g3k27vivfcw75zjxdb2tg2wpz3i4cdiyhxyd.onion
Seems like a legitimate Blockexplorer. https://3xpl.com/bitcoin
Tor Link: http://3xplor3rzajysy4j5fi3g3k27vivfcw75zjxdb2tg2wpz3i4cdiyhxyd.onion
No worry for rating yet, if you are not sure how to rate it, take your time until you know.
We don't have any time limit on this.