Patching scsi.device and using SFS or PFS3 or similar makes it safe to store files on the partitions. But it does not magically remove the 4GB problems from all programs.
Workbench is one of the programs which tries to calculate the amount of free bytes with 32bit numbers. 17,179,869,184 just does not fit into a data type whose highest storable number is 4,294,967,295. Everything above that is cut off.
You will experience similar problems with many other programs. Copy programs might tell you that there is not enough free space to save files although there are gigabytes free and so on.