Why an all-in-two exists
It solves one specific problem: the pole top cannot carry the panel.
All-in-two splits the light head from the panel, but keeps battery and controller integrated with the head. The reason is physical: on a narrow pole, a heritage street, or a site where the pole must stay visually slim, a full all-in-one housing cannot be mounted without either a bigger pole or a bracket that looks wrong.
It is also chosen where the light has to sit under a canopy, a bridge soffit or a building overhang while the panel sits outside in the sun. In those cases the separation is not cosmetic — it is the only way to get both a lit surface and a charged battery.
The trade is one more cable run between panel and head, and one more bracket to specify. That is the cost of the flexibility, and it is worth being explicit about it in the quotation.