In this day and age of internet, real time synchronization is clearly an excuse.
Google Docs, OneDrive, etc. they all provide offline mode. QBO can easily create a system where an offline lock is applied and no one else can make any changes apart from someone working on it.
Once all the changes are made and the application is able to connect to internet, all updates are uploaded to online version and open up the offline lock to allow everyone back online.
