What would you want to happen if you changed data synced into Fibery? Change it back in the source app (e.g. Hubspot)? If so you want Bi-directional integrations/sync. If not I am curious to know what would solve your need. 
I think in general the point of syncing data 1-way (as is the case with most - but not all - current integrations) is to link to/operate on that data for other purposes. E.g. link a Hubspot Contact to one in Fibery, or to an internal issue tracker for software dev, or use e.g. a Lookup field to show Hubspot Contact fields on a native Fibery Contact, etc.