Don't mix between what is:
Eligible for arena title
Eligible for a ranking in ladder
Title requires certain amount of games played and certain ranking (Gladiator is 0,5% and 50 games played, Grievous Gladiator is 0,1% and 50 games played)
Titles cutouts are based on amount of players on the ladder, so taking lowest rated player on a ladder and dividing it with either 200 or 1,000 we get cutouts for Gladiator and Grievous Gladiator, just like before the one massive ladder show'd up
Ranking in ladder requires you to have at least 1 rating and after that, you are on the ladder, which counts you in towards the percentages.
There is nowhere stated that you need certain amount of games played to have a ranking.