Moving dynamics onto the staff

[Knute Snortum]

I am confused.  While trying to find a way to move a forte mark up onto the
staff, I came across some very counter-intuitive code:

%%%
\version "2.24.3"

{
  % Why does this work...
  \once \override DynamicLineSpanner.outside-staff-priority = ##f
  \once \override DynamicLineSpanner.Y-offset = -2
  c''1\f

  % ...and this does not?
  \once \override DynamicText.outside-staff-priority = ##f
  \once \override DynamicText.Y-offset = -2
  c''1\f

  % And neither does this:
  c''1-\tweak outside-staff-priority ##f -\tweak Y-offset -2 \f
}
%%%

So why would overriding the dynamic line spanner's outside-staff-priority
change where the forte goes?  Isn't it DynamicText?  If anyone can clear
this up for me, I would be very appreciative.

--
Knute Snortum