Hi,
I checked my new phone in the charger that killed the old one and indeed does still go fast regardless of the setting. I left it few minutes as I am not willing to go again on the same process. I will open a support ticket for this. Also I will try another fast charger I have a home.
Adding the screenshot of from my Xiaomi fast charger (2020)
And my usual charger (Huawei slow charger from 2017)
Eco mode is indeed not working at all.