Thank you for your answer. So if I have a block level backup set of 4 files, (files A,B,C, D) and only one file has changed (file C, by example) since last full backup and time comes and next schedule full backup is fired, only file C is uploaded to build the new full backup?
Even more, only changed blocks of file C are uploaded? CMB is syntheticfull backup capable?

Could you clarify the statement of WillR "When the block level backup does a periodic full backup does it upload all files or only those that have changed since the last full backup (the latter I hope)?"