From different s3 release (3.0.4, 3.2.1, 3.4rc1) I tried :
smbclient \\\\s4server\\share -U DOMAIN\\user
I tried with files of a few megabytes to a few hundreds of megabytes.
Resulting file were either 0 bytes or a few hundreds of kilobytes.
I think the version numbers for SAMBA 4 Alpha/TP aren't worth to keep since we don't support any versions longer yet. Because all bugs filed will be propagated from version to version until they are fixed (for now at least) this field isn't necessary yet.
Fixed in 1937ab3668e6a4667ac4334a6e1bea2cc75cfb1d
The problem was caused by large reads in S3 smbclient not being honoured in S4