The design made by some FEM softwares for reinforced concrete members, sometimes result in less area of reinforcement. This does not mean that the design is not valid! You may need to check if the concrete tensile strength is counted in the design stage by the program. fctm is the tensile strength of concrete which equals 0.70 ? fc as per the ACI and we normally ignore this small value when the steel reinforcement is involved as it has no significant involvement in strength compared to that provided by steel bars.
Concrete tensile strength is one of the magic functions in concrete. Sometimes especially for pipes encasement and manholes up to certain depths, concrete might work without the need of reinforcement because of concrete tensile strength is quite enough to resist the forces induced by earth pressure, live loads, etc.
This may lead us to avoid adding the waterproofing membrane which will have no function without reinforcement and save time and money!