ᐅ Is a roof or canopy necessary for wheelchair-accessible patio doors?

We have a sloped plot that is currently developed. To put it mildly, the slope is quite significant. For the existing buildings (garages, cellars, and stables), the slope was excavated as much as possible at the time, and the buildings simultaneously serve as slope support. I hope this is somewhat understandable. We imagine it like this: at the ground floor at the back, a concrete wall = new retaining wall, and the other three walls are system walls from prefab house companies.

Provider 1, using solid wood with insulation applied on the outside, sees no problem building directly against a new retaining wall, including the seal between concrete and solid wood wall on the upper floor.

Provider 2, using a timber frame construction, sees a long-term issue with the sealing at the connection between the upper floor system wall and the concrete wall. Therefore, they propose building a retaining wall and placing the house at a distance of 1 meter (3 feet) with four regular system walls. We don’t understand the problem Provider 2 sees. This would have to apply to every connection to a cellar, wouldn't it? Is there any truth to this?

We want a level, wheelchair-accessible front door and a wheelchair-accessible patio door. Provider 1 suggests a large, solid canopy to prevent wind-driven rain from pushing water into the house. Provider 2 does not consider this a problem; if we want a canopy, we can simply add a small glass cover. Are there long-term issues with water infiltration through barrier-free doors?

It would be helpful if someone could answer these two questions. We are a bit confused since the opinions of the two providers differ quite a bit.