crescendo/diminuendo lines take vertical height from hairpin settings rather than dynamics text settings
Came up in https://musescore.org/en/node/88836
Via Style/General Style/Hairpins,Voltas,Ottavas it is possible to change the Default vertical position of hairpins, but these work for hairpins only, not for crescendo/diminuend lines.
Affects 2.0.3 and 2.1, but not master (which has a different problem here, see #164791: Style setting Above for Hairpins doesn't work)
As the positions do work in master, I think this is a bug and not by design, introduced when (de)crescendo lines got added in 2.0.3