I think the blurb from the article below will answer your question. I interpret it as you lose the ability to make these updates with smart campaigns by activating the campaign synch feature.
https://community.marketo.com/MarketoTutorial?id=kA250000000KytlCAC
CAUTION: Syncing your Marketo Program with a Salesforce Campaign skips the followingSalesforce Actions if they are configured within the Flow of your Program's Child Campaigns:Add to SFDC Campaign, Change Status in SFDC Campaign, Remove from SFDC Campaign, and Sync Lead to SFDC Campaign. Program to Campaign sync automatically takes care of these data updates.