No, it's an outfit called Bestforbritain.org including such luminaries as Carol Vordeman and Naiomi Smith who have been organising the official-unofficial tactical voting advice for a little while now, including the recent council elections.
That would only be because they are the only other large party. So for the majority of people/constituencies they are the best alternative if you want to vote to get the Tories out.
All they are doing is comparing the voting at the last general election, polling and then using that two give an option for the best way to vote them out.
Not sure what pro labour facts you think are on there
What do you want about I know constituencies where they recommend the liberal democrats.
The reason it appears to have a Labour bias is that reality has a Labour bias right now. It isn't an unfair bias if it's just reflecting reality, you not like it is immaterial.
I can't see any mention of stopthetories.vote in that discussion though so perhaps it's better than the others, at the very least it appears to give the poll data so there's some transparency there