Hmm, not sure what you mean here. I haven't removed the check - and in fact when I go through the code, the contentStream.length is being checked in the progressBlock, whereever we use AlfrescoContentStream.
However, for create/updateContent methods using AlfrescoContentFile, the length is indeed not checked. In fact, this is the way the SDK has been before. The rationale being, that when creating/updating a contentfile, we compute the length when we initialise the AlfrescoContentFile. So it should be a known quantity and non-0.