hello! Could you confirm me that before 3.23, UMIs were NOT taken into account by the alignment/quantification pipeline, therefore the UMI step in post-processing was "only" for QC?

Where did you get this info from? UMI support was added gradually and e.g. a position in R2 was for a while not yet supported, but latest ~3.9 ish should have had all the features for a proper deduplication using UMIs in place.