The particular stick definitely does not matter. Every problem I've ever seen is the controller on the server side. ISOmorphic's installation environment has long had a really old kernel which predates USB3. Since R80.40, it should be able to drive older USB3 controllers, but may still have trouble with USB3.1 or USB3.2.
The server's boot ROM can drive its built-in ports. It probes for storage and tries to find a boot block. Once it does, it hands execution over to that boot block. In ISOmorphic's case, this then uses the firmware's drivers to load the second stage of the bootloader, which then fetches the kernel RAMdisk image, starts the RAMdisk, and hands execution over to the kernel in RAM. That kernel then tries to mount the storage using its own drivers, but it doesn't have a driver for a USB3 controller.
Some USB controllers present themselves as a single device which can do USB2 or USB3. If it's only a USB3 controller, the kernel can't talk to it, so it can't see the storage, and all it has is whatever is included in the RAMdisk image. Others present USB2 functionality as a separate PCIe endpoint. If the server's USB controller presents itself as multiple devices, the USB2 controller may work. This sometimes requires the drive also be only USB2, but any USB2 stick would work.
For open servers, I've used ISOmorphic in the past, but I usually just use the LOM. It's slower, but always works. No dependency on hardware implementation details I can't control.
