Historical Rules · 13 July 2018
Rule 508.4
Official source text from the 13 July 2018 Rules release
If a creature is put onto the battlefield attacking, its controller chooses which defending player or which planeswalker a defending player controls it’s attacking as it enters the battlefield (unless the effect that put it onto the battlefield specifies what it’s attacking). Such creatures are “attacking” but, for the purposes of trigger events and effects, they never “attacked.”