Hi M. Frary,
This may sound like splitting hairs, but I am trying not to, by saying that nursery soil and all its highly organic components, have a different means of holding nutrients and water holding ability.
That means you are correct either way with Nursery soil, but wrong if thinking about Bonsai soil. These modern substrates seem to be all inorganic with little nutrient holding so burning roots will be possible by any fertilizer system, with dry roots being the most in danger, as there is little buffer against burning etc.
And yes, you know all this already, so just making a point, not attacking you.
And sorry to
@Gary McCarthy for being off topic.
Charles