That "NORMALLY" of inserts of preset camber and to prevent slippage is common for
rally coilovers (
another example and
another). IIRC there was mention of such for eg. MCS coilovers, for STX rule compatibility or smth. like that. But
Normally even if slot hole is slotted for camber adjustment on aftermarket coilover, maker doesn't also offer inserts too. One should put (non camberbolt) bolt there at rough position one needs, tighten, and fine-adjust camber using other hole. Works for most, if not receiving heavy hits to suspension.