Help in understanding implicit block of src:ggml

Hi,

Can someone help me understand why src:ggml is blocked by

   "Implicit dependency: ggml ggml-cuda"

Nothing in src:ggml depends or recommends on src:ggml-cuda, it's the
other way around. The latter is an optional plugin for the former.

I'm seeing this first since the 0.18.0 upload, where I twiddled with the
autopkgtest dependencies. But I reverted that in the 0.18.1 upload, and
yet I'm still seeing the block.

Before that, ggml enjoyed the 2d migration window.

Best,
Christian