Text in this card:
"...or immediately after this effect resolves, NORMAL Summon it without Tributing."
I don't know why people can normal summon another monster after this summon. I think is a bug
its not bug bruh. blackwing can summon whole deck as long you have blackwing in your hand. after occupied your field with monster banish 2 of them and keep summon till no blackwing left.
But then it wouldn't activate Black Whirlwind. But I agree that the ruling is a bit confusing. But you can remember the following rule: If you do normal summon through a card effect, it doesn't count towards your normal summon. For more details, check the Wiki:
https://yugioh.fandom.com/wiki/Normal_Summon#Multiple_Normal_Summon