I was reading over at reddit i think, the spider stats match a 5e spider mob instead of the companion spider so it's likely the incorrect spider is being summoned and is an EA bug.
Unfortunately, even if that were indeed the case, Find Familiar and Summon Companion are supposed to summon a single creature not a swarm of creatures, so that would also be an incorrect implementation of those spells/abilities apart from also throwing off the balance of summons in general.
