Does iPhone Throttle 4G speeds when using hotspot / internet sharing?

[Zeov]

so currently when measuring my 4G speeds where i live, i get about 90-123 mbits of download directly on my iPhone 6 Plus, which is pretty good. But whenever i turn on hotspot / internetsharing (via usb -> macbook) i only get around 20-30 mbit, is there a logical reason for this? not that 20-30 is bad or anything, but 100+ would still be nice !