VMware has the following in the release notes for Vmware Horizon 7:

Selecting the Scanner Redirection setup option with Horizon Agent installation can significantly affect the host consolidation ratio. To ensure the optimal host consolidation, make sure that the Scanner Redirection setup option is only selected for those users who need it. (By default, the Scanner Redirection option is not selected when you install Horizon Agent.) For users who need the Scanner Redirection feature, configure a separate desktop pool and select the setup option only in that pool.

link: https://docs.vmware.com/en/VMware-Horizon-7/7.13.1/rn/horizon-7131-view-release-notes.html

I assume this also applies to Horizon 8, however it is not in the release notes. Would be nice if VMware would clarify. Currently, we only enable this feature for a specific group, but this involves additional management of a template / pool etc...