"Going forward, when a player wins a ranked battle and their ECR is below 50% at the start of the battle, their ECR will be reduced by 5% instead of the typical 1%. There will be no change to the ECR formula when ECR is above 50%, which takes about 70 battles in a day to reach, so this change will have no effect for the majority of players."

In my opinion this is not correct.
Yes it take 70 battles to reach 50% ECR if you start at 100%, but what will be the next day ?

If you play after 24 hours again your ECR is at 74% (not by 100%) and with 70 battles you would come down to less than 37% when calculating with 1% .

So to calculate this correctly you should start by 74% (50% + 24% for 24 hours rest) and than it take 39 battles to reach 50%, so I think you cannot play 70 battles every day, this you can do only once when you start at 100%, but on a daily basis you will be punished it you play more than 39 battles or I am wrong ?