I don't think so either ... and SA should never had put that in print. Anyway, there's no argument, just numbers. The measure of 'more radioactive than' is Bq/kg. (Total radiation? who releases those numbers? where's the transparency?)

According to the following article (and a couple I'm not citing), coal fly ash counts are on the order of 250-1000 Bq/kg. https://link.springer.com/article/10.1007/s10967-006-6966-1

Specifically, concentrated (fly ash) measures:

"263 to 950 Bq·kg−1 for 238U, from 142 to 605 Bq·kg−1 for 226Ra, from 133 to 428 Bq·kg−1 for 210Pb, from 27 to 68 Bq·kg−1 for 228Ra and from 204 to 382 Bq·kg−1 for 40K"

Anyone who cares to is welcome to cite the Bq/kg numbers for waste from nuclear plants. Go ahead, pick some. I think you'll find they are higher. And most coal doesn't contain any Pu.