That only looks so. Also v1 pulls the graph data from the remote site. But the big difference is the how it fetches the data. Raw edition v1 uses PNP4Nagios and fetches the graph as an rendered PNG. That means only the PNG is transferred from your remote site to the local web server.
v2 uses the enterprise graphing system. This fetches the graph data as ajax request in form of a json data structure.
The problem now is that if you move the mouse over the graph and click you fire the next ajax request and fetch the graph data again. These are easily 100 requests if you scroll a little bit inside the graph.
Here it is a real problem (enterprise and raw) in the direction of @elias.voelker or @sebkir
Single load of graph page is ok
Only a little bit moving inside one graph
With this it is clear if you access graphs over continents then it will not work.
Grafana as example only reloads the data after you submit the new timeframe.
Moving the mouse over the graph produce no traffic this is also different with CMK graphing.