I don't really think it mattered if they banned either Ascent or Haven they probably don't have very high chance to win either one against Furia who is pretty good on both. I think Furia is worse on Ascent than Haven giving SEN a better shot on ascent.
But at the same time how much practice would SEN have with the roles they would need to play ascent? The roles they played on Haven are much more consistent with what each person typically plays so they probably just decided on that.
if they run the normal comp, who is playing Kay/0? zekken or sacy probably? but how comfortable would either of them be since they have typically always played the sova on that map? How much practice time would they have for that? If they decide for a different comp they would need to put in even more work and time that this (MIND YOU STILL PRETTY NEW ROSTER, some people forget this current roster has been together two weeks or something) would probably struggle with.
either way its just a tough spot for the team and you can't really blame the coaches if you actually think about it for more than 3 seconds