Disconnected french drain under the ground - is it a problem?

[MarkWales]

The builder agreed to extend French drain in our garden - before it covered only small part of our garden. When workers came they discovered that the French drain we had was too deep and was not optimally located. So what they did instead - they dig another one just a bit closer to the house and closer to the surface. They disconnected the previously build one from the site drainage and just left it buried in the ground. Old and new French drains are parallel to the house and located about 2.5-3 metres away from the property.

Is it fine to leave the old French drain as is or I need to push builder to remove an old one?
Did it create possibility of structural issues for the house?

Thank you.

[New Home Expert]

As existing French drain for the site is now disconnected where is the water at the disconnected end going? The only way is UP!
This will cause flooding at the surface at its lowest point which could be adjacent to your house.
The new French drain is purely to drain the area within 3m from your house so it complies with NHBC standards.  Depending on levels and gradients of your garden you may well still have surface water flooding beyond the 3metre mark which is not covered under the warranty.

As for structural issues, this will be determined by many factors such as type and depth of your foundation, and classification of sub strata and location and species of trees with roots near to you property.

Who is the housebuilder?