That is the advise I got before, but I find this is super difficult to hit the right temperature. I either get boiling coffee, or luke warm.
When you get used to the microwave you have, you can hit the same spot every time. It's a formula depending on your cup, the wattage of he microwave and time.
I can hit the temperature I want every time on a Bosch microwave from 80s which has two power levels and a rotary, mechanical timer.
Also volume of liquid and temperature of liquid and cup.
I generally fill the cup to the same level, and fill it from the same source in the house in 99% of the time, so they are implicit constants in the equation, at least for me.
It’s also helpful to know where the standing waves in your microwave are. Put a layer of shredded cheese on a big tortilla (so you can eat it and it’s not a waste) and run it till it melts the cheese. Observe where the cheese is melted and not melted. Put your coffee cup along the same band of melting. That makes your heating more consistent. Fortunately, mine has it’s strongest focal point dead center (which, I suppose, is not a surprise from a design perspective… still good to know).