>>13446495Out of manga adaptations I'm currently watching that didn't have pilot OVA/special of any sort:
Aku no Hana
Aria the Animation
Black Lagoon
Fate/kaleid liner PrismaIllya
Kami nomi zo Shiru Sekai: Megami-hen
Kiniro Mosaic
Poyopoyo Kansatsu Nikki
Saki (rewatching)
Saki: Achiga-hen - Episode of Side-A Specials
Shingeki no Kyojin
Toaru Kagaku no Railgun S
Uchuu Kyoudai
Watashi ga Motenai no wa Dou Kangaetemo Omaera ga Warui!
The only ones which fit your theory are Kiss x Sis, maybe you could consider TLR Darkness OVA (but it started as TLR TV series). There's also JoJo which had OVA before but it's completely unrelated to TV series.
So, shut your retarded mouth before you try to spread misinformation next time.
Pilot special/OVA happens but IT IS RARE. Most of OVAs come out well after show airs on TV.