This is actually a good question.
It’s about this one:
/* to give to transform */ RNA_def_int(ot->srna, "mode", TFM_TRANSLATION, 0, INT_MAX, "Mode", "", 0, INT_MAX);
…but I can’t tell at a glance exactly why this needs to be passed along to the OT_transform. Browsing history it seems its cousins were at one point or another removed from other operators. Does it actually serve a purpose? Does it have to be in the UI?