Do we need a lifting system as the architect suggests?

Because the connections of the channel are deeper than the base plate! Oh yes, concerns parcel 2

Now honestly... are you the expert or your architect?
The correct answer would have been (if it is a new development area):

"If the development work is completed and the levels are confirmed, then you need a sewage lifting station."

Your architect has no interest in pushing a lifting station on you. On the contrary - the planning becomes more complex. So relax and let the professionals do the work. Checking is good, but the question of whether and why a lifting station is necessary you should not ask us, but your architect.