rehearsalMarkFormatter => markFormatter in 2.24.0

[Richard Shann]

I've noticed a name change in 2.24 where
rehearsalMarkFormatter has become markFormatter.
I want to make scores that can be compiled under either 2.22 or 2.24 so
I tried this:

8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><
\version "2.24.0"
xxx = rehearsalMarkFormatter

%\version "2.22.0"
%xxx = markFormatter

\relative c'' {
  \set Score.\xxx = #format-mark-box-alphabet
  c1 \mark \default
  c1 \mark \default
  c1 \mark #8
  c1 \mark \default
  c1 \mark \default
}

8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><
If the commenting out is switched round this continues to work.
(The definition of xxx would be in an include file in a versioned
directory).

My question is, is this a reasonable approach? 
Specifically is it reliable to use variables in this way, as components
of a property?

Richard Shann