This isn't very surprising. Intel has already been making their GPUs at TSMC for quite a while now (I believe using N4). Porting and validating that GPU to Intel fabs would be expensive and take a lot of time.

There is talk about the next version of Arc using 18a. If it does, I'd expect Intel to move that generation's compute tiles to 18a as well.

I guess that explains why the current intel GPUs are actually good value and somewhat not terrible.