Ah, yes. Thank you, @rslu. Gerard @montarou posted another thread, to which there was this reply: How to modify a geometry using messengers in interactive mode - #12 by allison. There was the same conclusion - for a “minor change” (the second case), you need only change the geometry, then
/run/reinitializeGeometry
/run/initialize
Of course, the user has to take care not to cause geometry overlaps.
I’m not sure why one has to initialize after reinitialize.