Unfortunately this is probably a property of either your enclosure's controller or the HDD's internal firmware. Spinning metal generally wants to sleep so that the physical components don't wear out as fast. There are software solutions for Windows/Linux/Macs that act as workarounds, but nothing built into or configurable directly on the drive.
That being said, whether or not USB Loaders GX should be crashing like that is a different matter entirely. Normally I would expect reading the filesystem to wake the disk, but I'm unfamiliar with whether a specific instruction needs to be sent to do so. I'll defer to someone more experienced with the software stack for more details regarding that.