Make the basement smaller because you want to insulate from the outside?

Hello everyone

We have the following concern:
We plan to insulate our basement ourselves together with our neighbor, additionally from the outside with 10cm Styrodur.

The basement is currently planned in such a way that it aligns at the top with the insulated wall of the ground floor and upper floor.

Our construction company now suggests making the basement 10cm smaller so that with the additional basement insulation we get alignment again and no water can run between the house and the insulation.

Does anyone here consider this sensible? We have heard so many different opinions on this and are now totally uncertain.

Many thanks in advance.

Best regards

Hello, I consider this not only sensible but also a commonly practiced method to have the masonry, for example, extend over the reinforced concrete basement. I would even let the first two layers recede.
Regards Ronny