The lead designers of Super Castlevania IV, Bloodlines, Contra III, Hard Corps, etc. are employees of Konami, or were. I don't think (m)any of the lead guys for any of these games went on to be a part of Treasure, although yes, Treasure was founded by ex-Konami employees. So all of the games mentioned are Konami games, not games made by Treasure people. I'm sure they were involved with the games (programming, etc.), but not in a "key creative" way like direction or any of that (although back in those days, with such small production teams, certainly one programmer contributed a lot in that regard). Nobuya Nakazato, who supervised Contra III and Hard Corps also made games like Rocket Knight Adventure and is to my knowledge still at Konami. That and Bloodlines and Hard Corps were made after Treasure had formed, so...lol.
I like Treasure, but I think it's a stretch—and also false information—to say that any of those games are, in essence, "Treasure games," particularly since the main creative forces of those games didn't leave to form Treasure, and continued making games at Konami for quite some time.
Also, I equate Treasure games with goofy controls and, well, goofy everything (quirky)...and Castlevania IV is a very well-polished game with super tight controls and design and everything.