zeroing Fluid filled transducer on EVD?

I have a questions about the different policies on zeroeing the fluid filled transducers on EVD's I have worked for 2 different hospitals one in Dallas and One in houston. i have been doing NTICU for 10 years now. Both I have worked in we have worked with Integra's drainage system. Well Hospital policy at both hospitals had us zero and level at EAC the fluid transducer which was zeroed to atmosphere, just as we do the ART lines CVP ect. at the begining of each shift. Our EVD systems are open to drain from 0CM H2O - 20 CM H2O above EAC with hourly clamping to monitor. The only thing is that we have recently had a policy change at the present hospital I work at (the one in Houston) and now we zero completely diferently than before. Zeroing the old way as we do an art line and CVP lines made sense to me. Now the new way, we zero the transducer (which is filled with NS) and it is open to the CSF above the patient where it drips into the buretrol.
My point is that when we zero an art line the for example there is a one way valve that leads to the pressure bag that you have to release and above the transducer there is a threeway stopcock that is turned of to the patient. to zero, hence the transducer is the only thing that is being oepened to air (atmosphere) and being leveled. MEaning tehre is no interferecne from the pressure from the pressure bag becaseu of the oneway valve and no interferece from the patietn because the stopcock is off to the patient. I open the system to air by removing the syringe from the threeway stopcock. Sorry I know this is redundent to explain zeroeing and art line or cvp, but when done correctly and you know you are doing it correctly you can flick the tubing while you are zeroing, if there is no pressure interference by you flicking the tubing then you know you are correctly zeroeing only the transducer to atmosphere at a specified level.
Presently zeroeing the EVD system the new way if you flick the tubing with your finger while zeroing the transducer you get interference on the monitor while zeroeing, ontop of it being open to the csf in the line as well as the saline in the transducer, meaning we zero the transducer with saline and CSF now.
Or am I being to anal and none of this really matters we are just to do what we are told without and rationale.