If the policy was applied, received and enforced than yes... Silly question, did you select workstation or server from the drop down in the ePO policy?
If the policy has been applied to the correct OS type, drop down top left, it should apply on the next Agent Server Communication Interval (ASCI). This can be accelerated by sending a Wake Agent command and seleceting Force Policy and Task refresh check box.
Could I also suggest that you identify the name of the Jenkins process and use the On Acces Low Risk Policy rather than the On Access Default Policy to whitelist those folders for the Jenkins process rather than all processes. This will be more secure and this is what we have done in our enterprise.
We have also whitelisted the build processes on the devs machines to speed up the build process saving 25% of time.