No, I always remember it being a forge mod, since the 1.15 days at least. Not sure what to tell you. Maybe they discussed Fabric but went with Forge in the early stages? Maybe you're thinking of being frustrated with it not being a Fabric mod and having to install Forge? Maybe you're thinking of another mod entirely?
I think it was originally on Forge based on my memory where I was disappointed after seeing the trailer and trying to play with it. I couldn't though since I was using Fabric and didn't want to use Forge.