Depends on how you look at it. She is compiling her notes and writing them up to release on pottermore, yes. She is not writing any new harry potter books at all.
When she said she wrote his bio she meant before, when she was writing the books. So she’s already got it scribbled down somewhere. Same with Sirius’s entire childhood and the black family tree going back hundreds of years (my cries. i want to see it on paper so bad. you cant get any info off the one on the wall at grimmauld place)
but yeah i hope that answered your question!