Winding tfmr's. Heater windings.

[Kalee20]

To me it would appear that the tap is physically in the hole through through the middle making the lead out wire become part of a turn.
I think you are stuck without using a laminated transformer where the half turn can have the lead out run around the outside of half of the core.

Refugee is right - you can't have a half-turn with a toroidal transformer (at least, not unless you drill a hole in the core).

With a laminated transformer, you can - if you have the start and finish coming out one side of the lamination stack, you can have the CT coming out the other side.

However, it is not to be recommended unless there is practically zilch current drawn from the half-turn terminal, because you get flux imbalance between the two outside limbs of the transformer, and this manifests itself as high leakage inductance. You can add flux-balancing windings which fix this, but it's all getting complicated now.

Best way with a transformer-from-scratch, is design the low voltage secondaries first, round them to a suitable integer, then fine-tune the voltage by selecting appropriate primary turns.