I never actually expected the first penetration to be not from Kazuha and be Futanari. At least this can shut up some stupid individuals that kept saying that Sunao had actual sex with Kotetsu which was "hidden" from us. Like the author wrote "no penetration" clearly and when he finally wanted to show us sex, he went all out with this one. Some ppl man... Really stupid.
The first time the author used No Penetration it was when MC was woken up by Kiriha in the morning. Decensored version literally shows penetration. Btw, the decensored versions are fans who follow him while he's drawing the pages, and take the images as he finishes drawing them b4 he gets to the censorship process.
Author has been using it as a white lie to show intercourse while escaping the manga editing board.
Recently though, Seinen have been given leeway to show intercourse as long as the whole story isn't just straight up porn, so now he's stepping back from that. Think Parallel Paradise.
It is objectively the case that these girls were getting fucked, but he was just "hiding" it, so he wouldn't get in trouble.
After the Sunao case though, he lost a lot of fans and is backpedaling.