This only is true if you accept that additional money gets equally shared; however additional money benefits those with assets the most, whereas those with fewer assets (the middle and lower class) are punished in inflation as they are dependent upon income which often does not change in response to inflation.
Or in other words, if I have multiple properties, stocks, investements etc, inflation is good for me because those things increase in value; however if the primary source of capital I have is a paycheck I get each week that I then have to immediately spend on housing, food, groceries, gas etc, inflation hurts me because my boss isn't going to raise my pay, meanwhile everything has gotten more expensive in the meantime, and if my boss does eventually give me a COL increase that will have lagged to the point the rest of the economy has already caught up with it.
Pretending that inflation is good for debtors is like pretending that economically speaking we are all spherical cows in an airless frictionless vacuum.