I think by dt*fade speed, its refering to delta time multiplied by fade speed, so the fade effect is not dependant on the frame rate.
I think so, if i understood you correctly.
Here is a link with more info, is for Consturct 2 tho.
https://www.scirra.com/tutorials/67/delta-time-e-independencia-de-tasa-de-fotogr...