A laptop is considered a PC as far as Webpage designers are concerned. They will send the page complete with all the bells & whistles. Your browser may be set to pre-fetch page links as well.
The laptop sees your hotspot as a WiFi connection so it will behave as if the sky is the limit bandwidth wise even though the WiFi connection is being supplied via a Mobile Data resource.
A mobile device is seen as a device that should get content that is compressed and with some of the fluff stripped to conserve Mobile Data bandwidth, so Tablets/Smartphones have much smaller bandwidth appetites.
You might consider fiddling with your browser's User Agent parameter to get the web to see it as a mobile device. (Back up the original first though.)