if your father played Czerny for pleasure, that would be pretty unusual.

That would be my father.

What you say here makes sense of this to me - that Czerny exercises are "prescribed".
These are likely exercises my grandmother would have assigned to my father, whose
piano education was sporadic - my grandmother would sit him down for a lesson at whim it
seems. Not to be too heavy-handed about this, but my father was certainly playing
"for" his mother here.