Eaves height of a three-gabled house (bay window/extension, ...)

Then it seems illogical to me

I think we mean the same thing, but we are not speaking the same language. "Just over there" does not occur in geodesy, so here is another attempt at visualization:


Top edge of finished floor = top edge of finished floor

Since the dormer is not subordinate, both the eaves of the main house and the eaves of the dormer must remain below 6.25m.
And to prevent another misunderstanding, my sentence

In NRW, at least, this one-third rule does not apply

referred only to dormers. For the subordinate building recesses mentioned in the development plan

Subordinate building recesses are not affected by the specification of the eaves height.

the one-third rule from §6, sentence 1, 2.a) Building Code NRW could be considered to assess the subordination.