Batteries have a constant charging speed from 0%→70% instead of being any faster at 0%?
Maintaining the exact same charging speed from 0% to 60% batterlevel is in my opinion a bad design choice. Yes it charges your battery faster but it also puts more stress on it. At least these phone slow down the charging above 60% to 70 % and that's a must.

It is generally recommended to only fast-charge Lithium based batteries (practically all phone batteries are Lithium based) at a charge level between 30% to 70 % (maybe 20 % to 80 % is ok-ish as well).

When a Lithium based battery is below 30% or above 70 % charge level fast-charging puts extra stress on the battery and this causes wear. So do that often and the battery will wear out sooner.

So a properly designed phone will only charge at maximum speed when the battery is not at a too low level and not almost full. If a phone does not do that then it is not treating the battery for optimal lifetime.

Source: Battery University and others.