Manifolds are definitely part of what we call "Best Practices" when installing pressure or differential pressure transmitters.
It will increase the longevity and maintainability of the transmitters.
Longevity will increase because with the use of a manifold you can easily isolate your process from the device in periods that you are installing, testing or even cleaning your lines. In this way you will avoid exposing the transmitter pressure sensor to impurities, over-pressuring above limits and from possible corrosive acids substances.
Maintenance wise, it will be easier in a time-schedule to verify and adjust the transmitter zero by only handling the valves.
Manifolds will also make the removal of the transmitters easier. Close the valves to the process and safely remove the transmitter. Now, take it to the workshop for deeper analysis.