Dear Augustin,
I might be wrong, but I really do not remember that appoggiatura was the default in an earlier version and that it became acciaccatura on more recent versions. I remember that the option was asked a long time ago, like in 2017… So this must be on the backlog somewhere, and it will eventually be implemented when it’s its turn 
I found this 2018 thread (but I really think there were others, before…) : grace note by default as appogiatura?