The history is 20. So after 20 losses in a row the matchmaking forgets it. 20 losses in a row is treated the same as 100 losses in a row. So your win/ loss/ tie rate can be anything from 20 wins to 20 ties to 20 losses in the last 20 wars.
Elo based matchmaking effectively has infinite win/ loss/ tie history ( in actuality it is target top divided by 50% K-factor or 100 in Empires raids ). So even if Empires war matchmaking worked, it should really track your last 100 wars.
And as Empires has shown, team based, and might based, matchmaking has problems.