Sonic Mania dev Headcannon clarifies that they didn't exactly work on Sonic Origins
Their work is being used, however
Sonic Origins, the upcoming collection containing remasters of Sonic 1, 2, CD and 3 & Knuckles will be using builds of these classics built on Headcannon’s Retro Engine, but the indie developer wanted to clarify that they did not actually work on Origins itself. Here’s what they had to say:
In short, it sounds like the collection will be using Headcannon’s ports of the classics, but the additional content original to Origins was all handled by internal teams at Sega.