Currently, some of the data reduction proxy's statistics, such as the amount of data saved, are stored in syncable prefs. See everything in: 

https://code.google.com/p/chromium/codesearch#chromium/src/components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.cc&l=32

On Android (and iOS) such prefs are not actually synced, but soon will be, which might cause some statistics to report on the union of all of a user's Chrome instances, or cause other undesirable behavior.

One way to accomplish not syncing this data would be to move to using the levelDB that is used with the data reduction proxy on desktop.